My bike is too small for me.
In '94 I bought my Trek 820 as an upgrade from a Huffy mountainbike. I knew next to nothing about bikes, sizes, etc. But it was a made in USA Trek, and it was alot lighter than the Huffy.
I rode it only casually on rides with the family, then later, for excersize, but it was replaced by a roadbike when I got more serious. Then my wife used it until she got her own bike.
Now, with other bikes in the stable, it seems "cramped" and I ride it with butt all the way back on the seat, hands on bar ends.
Lately, I've been thinking of making a gravel-commuter out of it, using a set of mudguards I bought for another project.
But looking at other 820s, I'm noticing how small my frame is by comparison. Being somewhat nostalgic, I'd hate to let go of an old friend, but at 5'8", 32" inseam, it looks like a frame one or two sizes larger would suit me better.

possible next size up will provide better feel / fit

but on this bike - the stem is fairly short with significant rise (upright) - and the nose of the seat is tilted down … a longer stem and leveled seat might provide better feel

The ugly truth of the matter, I always knew my bikes were too small as I have a 38in. inseam, when I finally realized I needed 66cm, 63-64 minimum for a very good ride, it blew me out of the water.

Had to quit buying 58-61 unless a great deal and something special.

Also came to find out that the more I rode the big ones, the more I needed them as my body and bones stretched out to fill them up and ride much better, it was quite a revelation.

the seat has been adjusted all over (level since pic) and what you see is the best I can get. I see what you're saying about the rise and length of the stem, but as it is, I feel very"face forward" on this bike compared to my others.

Bones stretched out is a good way to put it. I have a good stretch on my Raleigh Sports and Super Course, and they just feel right to me compared to the Trek.

I was always hamstrung literally and physically by too small bikes and worked around it with long and tall stems and SP's.

I used to go to shops and the "fit" guy would insert himself making some comment about having one or both too high, etc.

"Really?" I would say, so out came the plumbob, tape measure, protractor, etc then they would proceed to measure and always end up with something like "huh, thats right where I would have put them."

Never had any proper size bikes growing up so didn't really know any better but always made them fit the best I could.

My first good bike in HS almost fit when I got it but didn't after the next growth spurt, got a long Campy SP for a good deal but finally figured out it was a narrow rail so the seat was weird being a regular forced onto the narrow post, also got a 135mm 3t stem that helped a lot at the time but it had an odd effect too for being so long.

With a short stem with a lot of rise, I'm not sure a larger frame would be a good thing. Larger frame will have a longer top tube. You would be more stretched out.

A longer top tube is just what I need. Right now I feel very cramped and hunched over.

This is primarily a consequence of racing "back in the day", Italian fit was the go to default for a long time and much that followed as the monkey was efen the futbol to get the aggressive position that most wanted to emulate whether they actually raced or not.

Many fit systems catered to this and made it even harder to get comfortable on the bike for touring, joy riding, commuting, etc.

I never raced or cared and would never have been able to get serious the way I'm built and my lakadaiscal attitude about racing bikes.

Drag racing MC's is a whole different story however.

It hasn't really changed. A slammed stem is the Way of Manly Men

With the saddle tilted down like that will make you put more weight on your hands giving you that sensation.

Yeah, that's exactly my point, we're still hamstrung by the past and I get it, if you drank the Kool Aid and it worked for you then you were golden, especially if you were strong, tough and fearless enough.

Like I said, not my jam but the drag racing was pretty much the same in that way, many, many azz whoopins delivered and received, not for the whimpy or faint of heart at over 100 mph round after round, race after race, season after season.

Believe it or not, but one problem might be that the cranks are too long. I had a bike like your Trek, and I couldn't get it right. It had 175 mm cranks as is common on MTBs.

I don't know how you can ride with the saddle tilted down like that. Can you even sit up and ride no handed?

Which way does your handlebars need to move? Have you tried changing stems?

Going to a larger frame would move the handlebars away from you, which would result in you hunching over more.

Nothing wrong with moving your friend along to someone who will fit it better and appreciate it. I hope you find a bike better suited to your cramped spine.

Other than moving it on,

1. Straighten the saddle as mentioned and get an adjustable set back seatpost.
2. Maybe use some sweep back bars (rather than the mostly straight.)
3. Save it for that special person who will come along and think it’s the best bike evaaah!

The saddle has been leveled since that pic was taken, along with other adjustments to try and make it more comfortable. I believe the seat is as far back on the existing post as it can be. I can google setback seat posts.
it would be nice to find a slightly larger frame to at least try out. 820s are plentiful and cheap enough.
I found this one for sale locally. I'm guessing a '91 or '92 by its features.

Looks to be one size larger than mine

If you are going to look, you might consider looking at Multitracks. If you can get your hands on one in your size, they are great gravel-commuter types (cantis, but also 700c tires with room for 38 wide and some change).

I was going to suggest using riser bars, as is quite normal on today's bikes. Only drawback is the possible need for longer cabling, especially as such bars tend to be wider.

And making sure that you aren't height-constrained by a too-short seatpost!

Also seconding the suggestion to consider shorter cranks if your legs are feeling overworked or if your saddle height seems like a difficult adjustment decision.

I don't think that the saddle needs to be moved rearward. Possibly/likely raised, but today's mtb's all have much steeper seat tube angles than your bike.

Your stem has minimal forward extension length, so I think there is hope for achieving a good and proper fit (this coming from a similarly-proportioned 5'9" rider having a relatively long inseam).

I trudged out through the snow and took a closer look at what I have. Seat post to crankset measures 18", horizontal from base of stem to SP is 22", which makes the frame an 18'. This is about 3rd from the smallest according to the 94 Trek catalog. I'd need to go about 3 sizes larger to gain 1" on the horizontal distance - aka reach. But at that point standover height is at my uncomfortable max.
the SP measures about 35mm setback. Not sure I'd get much more setback than that.
so, to turn this bike into the gravel- commuter, I'll need bigger, gravel tread tires and add my Bluemel B65s.
Or, as jdawginsc said, pass the bike on to someone who thinks its the best bike evah! I have plenty of grandkids to choose from.

i think you could reverse the stem and slide the seat as far back as the rails will allow. also bump up your air pressure in the front tire (only) to about 60 bars.

that should do the trick.

870 psi?? And I thought I ran high pressure tires!

Vintage Trek says 1987 or '88. https://www.vintage-trek.com/model_numbers1.htm

By the color chart, it looks to me to be 91 or 92, but older is ok too.
I'm intrigued by this Antelope. Owner says its a 20" frame which would be one or two sizes larger than mine. The paintwork is a bit tatty but its black so should be simple to touch up.

you'll want to avoid "snake-bites" flats.