Are you asking about solid or hydraulic rollers.
As far as direct drop in. No way in hell were the comp hyd. rollers going to fit in my 360 roller block. The valley needed to be ground to clear the tie bar on the "Drop in Retro-fit Rollers". Of course the short block was already put together. Disassembly to grind, rewash and re-assemble was out of the question for me when alternatives were available. I ended up getting the stock MP rollers, spiders and dogbones.