I am trying to preserve the drivetrain in a dinosaur, but a nice one. Any help on where to find these three hard-to-impossible-to-find items would be greatly appreciated.

Long story:
Soon I will need service my '82 Stan Pike drivetrain. I want to make as minimal change as possible. I currently have a NR 52/42 and a Suntour Perfect 888 with 16/17/19/25/32 - this ratio has served me well for hills and touring since I built the bike up. This gives me a range of 88 to 35 gear inches with the existing 27" wheels, AFAIK.

Most of my riding is on my 19 tooth rear - and now it is almost at 0.5% wear. I've been changing out the 19T (I had 3 spares) when worn. Now, when I pop a new chain on, I have to ride gingerly for a week or so until the chain stretches a bit - obviously, not a great situation. I rarely use the 16 tooth, and occasionally the 17T.
I know that I could remove and replace with a new freewheel and buy and fit a compact crank (once I figure out sensible and available tooth combinations), but this is more change and expense than I want to commit to at this time. I have little space in my rented house, and no workbench or space for it. (I could also buy or build more modern rear wheel, and convert from 27" to 700c, but that means getting some Tektro or other brakes - I'm 3-4mm shy of having clearance, even with a drop bolt. - so I'd like to do as little as possible now. Otherwise, a complete refit is the next logical step, and I'd rather leave this for either when I have a workshop and plenty of time + dollars on my hands, or else leave it for the person who eventually buys the machine when I can no longer ride it.)

What I'd like to do is simply replace the worn 19T not threaded freewheel cog and 17T threaded with unworn ones, (that's all!). The 19T one I need are (I believe) Suntour "A" cogs - not threaded - with four semicircular nubs at 90° to key into lands in the freewheel body. But I'm not 100% sure the cog pattern is identical in the "Perfect" and "Winner" &"New Winner" freewheel models. I'm looking for one that will fit the Perfect model. The 17 is threaded - does anyone have this one to fit Perfect?

Finally, does anyone have or know where I can get an adjustable cup lockring for standard NR British BB? Mine has suffered torn lands - maybe my Sugino wench doesn't fit intimately enough - it has slipped off a few times now and I can't seem to find a replacement lockring - or the next overhaul will be the last with that BB set.

Thanks! BF rules!

Let me check my cog stash for a "Perfect" match or two and get back to you. If I recall correctly, SunTour made two slightly different sizes/shapes of "nubs," and one could easily use a coarse file to adapt one to the other type of body.

That's why commonly available parts are better. Many C&V parts can be difficult if not impossible to find. I think Sheldon Brown wrote that people looking for a museum quality restoration should keep their expectations realistic.

Does it have to be a NR lockring ?? Other brands would work.

This seller has quite a selection of Perfect freewheels. I've dealt with him and been pleased. Possibly he can help you out. Best of luck.

https://shop.ebay.com/paddythepeddler...dkw=&_osacat=0

No- I'll make do with almost any one- I don't want to buy a whole BB set and throw away everything but the lockring! That's all the LBSs have offered so far...

Hey Norman, on the contrary, I don't want to hang the machine up in my own museum (of one), but continue to ride it without rebuilding it... I'll hit 60 this year, still working, and I don't work in a bike shop. I'm not in the same position as was Sheldon, with ready access to a broad inventory of parts, and the dosh to acquire them. What's so unrealistic about asking the community if anyone has these?
At the time of this build, Suntour was the commonly available part, arguably better than Shimano at the time... (who knew that they would fail) With the hundreds of thousands of Suntour freewheels made, I figured that someone somewhere in the BF crowd, many of whom have shown bins upon bins of parts, might just have a stash of cogs in a box... which is why I write. After all, C&V'ers here make jokes about their compulsions...
And so far, thanks to John E and PastorBob for your responses!

I'd buy a 126mm Shimano cassette hub for dirt cheap off ebay and switch out the hub. You can reuse your old spokes and rim.

I noticed some Suntour cogs at Loose Screws... not sure if exactly what you need.

https://www.loosescrews.com/index.cgi

Thanks, dbakl. I'm aware of these - and the question I had for the group was whether any of the Winner cogs will work in Perfect freewheels. I don't think so, as the bodies and cogs were re-designed for the Winner and again for the New Winner. I don't know if any of the Winner or New Winner splined (not threaded cogs will work in the Perfect. In the former two, there were two different internal diameters of splined cogs, and the question is do either of these two fit the Perfect and if so, which one.
I will try to email the folks at Loose Screws to see if they know - they mention Alpha A, D, E, L, and S cog positions for their Winner cogs. Loose Screws states in their "Contact Us" page "Please do not ask us technical questions..." and "refer to the manufacturer or relevant technical information on our links page" but of course, there is no info on the position names for Winner cogs that I could find. They just say "If you are replacing a Suntour freewheel cog, look for the letter which signifies the position on the face of the cog." But Perfect cogs have no such signifying letter.

I have a Suntour document with a New Winner blowup from 1987, but the positions are not identified as Loose Screws does - clearly, there are two diameters of splined cogs and at least three different threaded cog types!

I have a Suntour Perfect blowup from 1976 - in this freewheel, there's only three type of cogs: splined (with the four nubbins, with internal diameter all the same), and two types of threaded, one with a built-in spacer, and one without.

Why not just a new, complete freewheel?

That's my suggestion. eBay is drowning in freewheels. I've got an extra one lying around somewheres and another on a wheelset I don't plan on reusing.

Then there are the new ones available in lots of places.

Cranky, given what you've been riding on and your favorite ratio is either 52-19 or 42-19; if you decide to go with the compact, get a 50-36 with a Shimano 5 speed freewheel 14-17-20-24-28 for $20

Thanks to all of you for the reality check... what brand(s) of crankset do you recommend that will fit the late 70's campag spindle - I've no clue about whether the tapers of new ones will fit?

They won't fit. You'll need a new bottom bracket.