WTH? Engine won't turn over after transmission install....

If You had the Clutch Disk in a bind. (Off-Center)... Idunno how you got the Input Shaft to go Thru it and still mate up with the Pilot Bearing?
Bell-Housing Must also be Centered to the Crank before you stab the Gearbox into it or you'll have bad vibes and then bad bearings...