Between the LS2 & LS6, what parts are Interchangable & what aren't? (Like the crank in particular) Thank you.

 

Pretty much everything but pistons and rings.

 

Look up crank reluctor wheels..they will technically work in either block but you need the right wheel for the computer you plan to use. Knock sensors need attention. Cam sensor/front cover is different though does interchange. Cams are 3-bolt vs. 1-bolt right? Just have to match up the right sprocket, cover, cam sensor to make it work right depending on which direction you go.