I'd be looking for a P2 2.4 or 2.5 litre with an M66 gearbox......
The later motor is so much better than any used motor you might find , reconditioning your motor is expensive too.
While M66 is a bit rare it has a better spread of ratios than the M57H in the R.
Your auto can be built a bit better and even paddle shift added , an old Turbobricks thread has it.
If you cut the oil cooler lines you can patch on an external cooler for bot transmission and engine oil, no need to plug the radiator just flush out the old fluids.
