May be a bit of a reach, but I am looking for suggestions on used hardtail frames (under 250 ideally) with relatively (67-69 head angle) aggressive geometry that would fit a 90's marzocchi bomber fork.

Have you tried Facebook Marketplace and Craigslist in your area?

What size frame are you seeking?

looking for model suggestions, thanks though

Whatever is right for 5.10

A '90s Marzocchi bomber fork will likely have been designed for a typical NORBA-geometry 26er hardtail of that era, unless what you have is some kind of dirt jump fork. So, again typically, head angle will be 69-71 degrees (w/sag). If by 'aggressive geometry' you mean something more typical of post-2010 hardtails -- long, low, slack -- fork won't be right.

So, what you should be looking for is a mid/late 90s/early 2000s 26er frame. Probably hundreds available used: Specialized Stumpjumper; Giant Rainier or XTC; Trek 4000 to 8000 series come to mind. That sort of thing.

thanks. Do you know of some 90s hardtails like you mentioned that are pretty capable of shredding?

Depends what you mean by "shredding". What is your fork's travel? If it's in the typical 80 to (possibly) 100mm range typical of the era, you're really talking about an XC (cross-country) fork/frame. But 'zocchi made some of the early 'downhill' -- even dual-crown -- forks; is that what you have?

If it's an xc fork, then the kinds of bikes (frames) I mentioned would be typical good fits for what you have. If you are looking for something more capable of taking big hits, 6-foot drops to flat, etc., you'd be much better served simply buying a modern bike designed for that purpose.

"shredding" what? If your starting point is a fork, you have to make sure that the frame is capable for the use for your wants. If you already own the fork, perhaps researching the bikes that it was usually mated to would provide a hint about what frame to attempt to buy. Second hand limits you to what is actually available. However, current equipment is far more capable that what was around over 20 years ago. If you want to "shred" your old equipment mat disappoint.

I already have a newer bike for this purpose. I want to build a bike under $200 to use as a commuter, and think it would be fun to have a hardtail. I know 100 mm isn't alot, but you can ride rock gardens on a full rigid if you are committed. I am just looking for a hardtail that would fit the 90s fork that was sort of an "enduro agressive hardtail" of the time period.

'Cool'! I get it. If your fork is 100mm, then the suggestions I made initially stand. There really weren't 'enduro aggressive' hardtails in that time.

You want to look for any sort of pretty standard 26er hardtail frame from the '90s through early 2000s. Tough is good; most were pretty tough: all the big mfgs. made 'em, in quantity. Me? I'd look for something like a Giant Rainier circa. '03 to '05. Tough as nails. Here's a pic of my '05 with, oddly enough, a 'zocchi 100mm fork.

'Agressive Enduro' wasn't really a thing 20-25 years ago. As far as higher-end bikes, you had (NORBA) XC bikes, and early FS / DH bikes like the Spec FSR, GT LTS, and Super-V

'Bikes like the GT Zaskar, Stumpjumper / M2, can sometimes be found mostly complete, and in good shape, if they havent been ridden into the ground yet.
You might be able to find an otherwise complete bike with a blown-out fork that you can swap your Zoke' into. Headshok equipped Cannondales are also good frame donors, since a lot of them got retired with blown shocks that were too hard to repair. Add a fresh (conventional) fork and a headset adapter, and you're riding.

You are going to shred your commute?
Shredding, whatever that is, and commute just dont seem to go together.

Why not? I regularly do fast trail riding as well as sometimes go over the mountain behind my work while commuting. It’s really no different than bikepacking. This bike

DSCN0934 by Stuart Black, on Flickr

meets Johnnyyuma’s criteria with the exception of price (the frame was more then $200) and is a very capable mountain bike. It’s in about the same time frame...about 2000...as he is looking for.

I’d say just pick any of the major manufacturer’s frames. Specialized, Trek, Giant, Jamis...whatever you can find. The higher end ones aren’t going to have places for racks but even that isn’t a detriment. I had a Specialized Stumpjumper Pro that had racks

93590004 by Stuart Black, on Flickr

I had to use P-clips but that’s not much of an issue. I don’t commute with pounds of gear so it was never a problem. I also had a Specialized Rockhopper

DSCN0167 by Stuart Black, on Flickr

The advantage of the Rock Hopper was that it did have rack mounts. The Dean above didn’t have rack mounts but I had them added...which is easier with titanium. Fleabay usually has any number of mountain bike frames that would fit your needs. A 18” is probably what you are looking for. Not sure where you are located but if you have a co-op in your area, they may have something too.

Why ??...what's wrong with seeking some urban obstacles and having a bit of fun on a commute ??...Sometimes I will detour and take longer route just so I can ride some single track after work,.

nothing is wrong with riding single track on a commute. I've done it with the bike I use, which is an old gravel frame.
I just wouldnt call it shredding.

Obviously, bikes used for commuting are varied. I assume a rack and pannier(s) will be used since clothes, food, etc need to be carried. It just doesnt conjure up images of shredding(whatever that actually means).

I think you are going to have a hard time finding a 26” HT frame designed to have a 67 deg head angle with a 100 mm fork.

There were 26” frames designed around that kind of HA, (what you are describing as “enduro hardtail”), but they were usually meant for longer forks.

And to be honest, I think modern enduro geo is not that great for street/road riding anyway (I bring this up since you mention commuting)

Of course, you could just “overfork” a mid 90s frame designed around a 60-80 degree fork and get a slacker HA, but you will also end up with a higher BB... which is counter to the modern definition of “shreddy”.