I have Alot of experience with that O ring.
I 'thought' that skinny one was where my leak was. So I got sloppy and in a hurry an mangle a finger between cam gear and head. Yep, known that area well...$20K in bills later and a finger I wish I would have finished off myself.

6 months after that fix I got around to going back thru the still leaking problem. The big leak I had ended up being the cam seal. Oil did not run on the inside under the cam gear or get on the belt. It was all over and around the distrib body adapter and running down behind AC braket.
The seal I replaced when I did the adapter body o ring was done wrong. I pushed it in a hair too far,,,just a hair.
I also have some wear lines on the cam sealing surface. My cams probably have 300k + on them though.
I'll look in my junk box when I get home. I have a coouple of those seals in there somewhere in the OEM packages, and get back with ya.
Another place of leaks on these is the contact area of the cam caps to head . It will look like the valve covers are leaking on the ends. A then coating of nut lock should be used as a sealant when you take cam caps off. The machine shop I used fogot this and a few other things ...

dave h.
'89 Raider V6 5spd;Aisin Hubs;; Gen2 LS: frt. brakes, rear coils;U.C.arms;R.trailing arms;idler arm; rear LSD axle w.disc brakes ;2 battery system for Dog's fan; relocated ECU; custom bumpers;J.Baker receiver;Conferr roofrack; t-bar crank.