Roller Block Cams?

So, is there a difference between a Roller Block Cam (1990-360 block) and a "Retro-Fit Cam".
I have a 1990 roller block that I intend on using with a new cam designed for the stock roller lifters, but all I seem to be able to find are Retro-fit cams, and hoo boy are they pricey$$$$.
Will a retro fit roller cam work with the factory lifters in the roller blocks? I'm thinking all rollers are the same but then again maybe the retro fit lifters are a different height/length than the factory roller lifters.