Mod's to BLI/Paragon Locos

I have several BLI/Paragon USRA light 2-8-2’s and 4-6-2’s, and would like to modify their valve gear. Specifically, I’d like to swap the valve gear between the two types. Has anybody done this? It seems like something that should be possible with a reasonable effort, but I wondered whether anyone out there knows of any potential pitfalls.