No start on rebuilt 360LA

Once you get the timing issue corrected, if the issue persists:
Compression check, as previously stated. With those rockers, your valve lash could be off or you may not have the correct pushrod length- could be holding the valves open a skosh. No idea what your build is, what length you're running, what block decking/head surfacing may have been done. Lots of variables.
Cam timing. As previously stated.