Hmmmm, I hadn't thought about that. I does seem like the dist. gear sits beyond the crown of the cam gear a bit. I put a brass thrust washer under it last time. I'll have to research the proper setup, I suppose. I'm thinking a shim under the flange.........have you checked depth possibly is pushing down to much on cam I always liked the collared dist..
No experience with olds engines but I have ran hyd roller and solid rollers sbc only time I had problem with gear was a bronze. I went back to steel never had an issue again.I would find specks on depth maybe your 2 deep.
specs called for a bronze for my retro CCHR300 1st few start ups and pushed dist out bronze gear showed wear after an hour..replaced with steel and bought a collar for dist never had an issuse again
Would I pull the distributor up while rocking the rotor back and forth until the least lash is achieved? Then measure the gap under the flange.... I can't imagine it needing much.