Have You Taken A Look At Schneider Racing Cams Lately?
They were a camshaft and lifter design that was the forerunner of the roller camshaft and lifter. Since the lifter face is larger diameter than the lifter body, they have to be installed from the bottom, but before that can happen, the block has to be spot faced at the bottom of each lifter bore, so that the increased diameter "mushroom"part of the lifter can have room to fit. Otherwise, the larger diameter mushroom part of the lifter would hit the bottom of the lifter bores.
Their benefits were very similar to that of roller camshafts. More aggressive lobes, better approach and departure ramps for better valve action. The camshafts increased aggressiveness, required a larger diameter lifter to handle. Larger even than the already over sized Chrysler .903 diameter lifter.
It's really old technology, but one of those cases where it really worked. You can make gobs of power with mushroom stuff. To my knowledge, the longevity issues were never worked out. They were so aggressive, they didn't last long, especially in lower RPM situations. If Schneider is bringing them back, that could be all worked out with modern technology. That would be cool as heck to have a street mushroom grind. LOL
