300D drive train mismatch

[Barrelhouse]

After a lot of preparation and waiting in line for a large block of time at the shop, they now tell me that the strong engine and transmission in the worn out '77 300D chassis
will not reasonably fit into the excellent '80 model that was brought in from the east.

The '77 had been sitting for a couple of years and the tech wanted to get it running and shifting properly before proceeding with the transplant. He found high compression and over all good performance though the car was coming apart at the seams otherwise. The engine had been rebuilt a few years ago. Does anyone know where the year/model line is where the transmissions and glow systems will match up with this 1980 chassis? I asked around before sending the cars to the shop and those I asked didn't see any problem. .well, there is a problem that will cost be prohibitive to work around. I would like to find someone that needs this engine and has the other. .some businesses do this but I don't know where they might be. I have a trunk full of pistons, bearings and a crankshaft as well as an oil pan and valve cover in the trunk to throw in not to mention an entire engine & fuel system (seized up) in the '80. I would like to restore the '80 and put it on the road for a while. Any suggestions would be helpful. Thanks!
Aaron