check LPE cam base circle then ur stock one, if LPE is smaller. lets say .025 then 7.425 should be good. if it's bigger say .025 then 7.375 should work. all this with using same stock size spring lift,rocker arms and lifters. now, I say should cause all engine are different. best way is to check is to "DIY". check out LS1HOWTO.COM .
I've got a 2001 WS6 LS1 h/c swap . I went with stock size p-rods. 7.400 after running it, heard to much of the "sewing machine" everybody talks about. switched to 7.425 . sounds quiet now

hope this helps some.
fuerzaws6