not sure if this is the right section. Any differences or weaknesses in the 99 6.0 block & crank vs. a newer model that should keep me from using it for my build?

 

The crank has a longer hub in the back and won't work with a M6 or 4L60e. You would have to use a Th350/400 with an LS1 specific converter with the longer crank snout. Also need a 6.0 flexplate (an older style 99-00 or a newer one and take the little hub spacer out of it)

No weaknesses that I know of. Mine rips.