M51 engine

I had a problem with my 1992 525tds engine and bought a s/hand engine from a 1994 car.The block on the 94 is different where the pump is fitted. There also seems to be an ECU mismatch as the 94 engine would not run with the old 92 ECU but would run rough on the 94 ECU that came with the engine (incidentally this ECU didn't run all the services i.e heater plugs) I've changed injection pumps with some modifications but it won't run at all. I've a feeling that the 94 engine came from a 325 tds as the loom is completely different and the sump well was at the rear where as on the 525 the sump well is at the front. If I change the ECU wiring loom on the the car for a 94 will that help?

very frustrated!