Later engine to earlier car... The fly wheel and clutch assemblies are different. The '77, I believe, is a single rail transmission, the '73 a three rail transmission. My wife's '74 engine was connected to a three rail transmission. You'll need the the early fly wheel and clutch assembly. The bolts that hold the flywheel to the crankshaft are different and the clutch plate is a different size, and uses different size bolts. As far as engine mounts and connecting to the bell housing there is no problem. The pre '75 shaft from the transmission is a ten spline shaft, the late single rail transmission shaft is a twenty spline shaft. I had to remember that you are doing the opposite of my operation. I hope I haven't muddied the issue. Call Nigel at Spit Bits, I'll bet he can help. T.T.