which tuner?
Prawn happily ran his K04-064 on an M3.8.3 for years. Made a solid 360hp and thrashed the balls off it.
The ME7.5 ECU is certainly easier to tune, granted, but the M3.8.3 can do the job.
You wont need oil sensor, but you'll probably have to tweak the wiring to use the old style temp sensor. Minor task.
You need EITHER a DBW pedal box, or a PFL S4 throttle sensor which attaches to the existing pedal.
You need clutch and brake switches from a DBW car, and the piece of harness that goes from the plenum box to the throttle and the brake/cltuch switches.
you need the DBW engine harness (APU will work, as well as the AWT one, but APU needs some modifications)
I used a TT ECU. Various others are available.
N75 the standard one works fine, and i had the N112 and N249 etc properly mapped out, so they're not fitted at all.
Wideband lambda needed
Boost sensor needed
I might have some of the bits if you go down this route. I think i have an APU harness, and i have an ECU that may or may not work.