Blackbok,
I read your post when doing a search on this rifle for info on the internet .This seemed like a good forum to be in so I registered so I could add my 2 cents.
I recently had aStevens "Buckhorn " 66B given to me by a friend of my wife who was nervous about it being in her house [it was her fathers]I offered to teach her about it and guns but no interest so she gave it to me.
It is a little rough ,but ,I've seen worse,and it's got extraction and feeding problems which 'm working on [$50.00 in parts] .They do seem like a finicky rifle but ,she shoots like a dream.The feed system seems the most finicky and this is "nearly" the same one used in the Stevens 87A . I have heard some people say some gunsmiths don't like them but my 87A works beautiful.
The bolt will come apart and it sounds like your trying at the right spot .I got mine apart to clean it ,but ,the rear section I did not mess with as its pin is a blind one and it looks like it has to be drilled out.
Mine has a standard 3/8" dovetail front sight and a rear leaf sight,also standard ,but ,It is drilled and tapped and milled for the peep sight also so I'll keep an eye out for that sight also.
Its finish is well worn so when I get it running I might consider refinishing it but I do have reservations about that ,even though it's not a highly collectable rifle and isn't likely to ever be one.
Where are the rollstamps on yours? Mine has a regular Stevens rollstamp on the top and a "second" more ornate "Buckhorn "one on the right side almost underneath the barrell which is strange as I saw another and it was marked "buckhorn" on the top position. Also,the Target sight version was actually supposed to be model No. 066 B but it seems to be an easy job to change sights as mine is milled for the target sight but marked as Model 66 B.
I'm sorry if I rambled but yours is the only post I've found on this rifle and maybe you have some info I don't know.I hope this helps!
Shootrj2003