Good luck on that one too. Back in the 80s my family's shop used to have a pretty nice stash of premium hardware like four bolt main small blocks and small chamber / large valve heads stacked up pretty high in the warehouse.

By the time they sold the shop in the 93 it was all gone.

I'm sure there still might be some old intact high end factory hardware running around somewhere but I imagine it would be like finding a needle in a haystack.