I think an engine transplant would be cheaper!
Many around. E28 parts is rather rare nowadays!
I am considering this route for one of my classic NK 2000.
Thinking of getting a M42 engine or M10S14 engine (wishful thinking!).
I was offered a half cut E30 @ RM2.5K with automatic gearbox ... maybe good if I want to make the car my daily drive. Hope the engine is a M42.
Another E30 M3 halfcut was offered to me at RM8k but with missing ECU, wire harness and broken oil-pan ... I donno, maybe this engine is the M10s14 that I am looking for, but the price is too steep.