I have the opportunity to buy a 1979 W123 300D with a bad motor (low compression). Would the motor from a 1976 115 body 300D be able to be put into the 123 body car?

Also, the 115 car has a bad injector pump (3 injectors aren't getting fuel). Would the injector pump from the motor in the 123 fit on the motor from the 115?

Thanks!