T56 in mock up. Will a T56 physically fit under the stock trans tunnel of a 68 Camaro? Yes. Will your driveline angle be so severe that you'd be nuts to leave it that way? Yes
This mock up consisted of a BBC mock up block sitting on big block frame stands with solid motor mounts, Quick Time bell housing, T56 and Bowler trans cross member. I also test fitted the engine on SBC frame stands and it seemed to fit better but either way, the moral of the story is that you'll need to raise the trans tunnel...life will be much easier and if you've come this far, why cheat now!!