So far I've found need to change intake maybe, bridge , mostly things to do with air to air piping.
Also see where somewhere they said you can swap a C5500 engine into a 2500hd but not the other way around due to engine mounts on the block.
I heard these were detuned but if running my current ECM etc shouldn't it carry over and run like the engine I'm pulling out??
Also up pipes , possibly manifolds and down pipe are different and need to be swapped.