1989 AUDI 100 C3 2.3 NF to AEL engine swap.

[supernintendo]

Hello, everyone!
I have audi 100 c3 with 2.3NF and I have decided that i want to swap a 2.5TDI into in.
For now i have disassembled my donor audi a6 c4, and pulled the engine out of C3. Also removed steering wheel hydraulic reservoir, because i'll use c4 steering pump and vacuum brakes - in my opinion the hydro brake boost is not as efficient. I will keep a/c from c3 (currently not functioning, but will try to fix that in the near future after engine swap. Alternator c4 - 120 amps instead of 90, why not? I have also pulled the wire harness from c4. c3 harness is almost out. Transmission will be the same that i have, yes i know, gearbox from petrol, it's short, it will be high revving, i know. I will change it out when i'll source a gearbox from c3 with 1T 2.5 engine, because i don't want to hassle with the gearbox mounts (Because of project complications for MOT)
So the problems - for now they're all electrical based:
*ECU - my donor is an auto transmission. Do i need an ECU from manual??
*Immobilizer - if it turns out i need ECU from a manual trans, what do i do with immobilizer? I've heard that if you do a immo-off, it does something funny with checksums in ECU - i don't want that.
*Tachometer - what do i do with tacho? If i will be able to source a c3 2.5 TDI tacho together with gearbox, then it's all good. But if not? Can i change only the tacho dial from c4 dash?

Thank you all in advance for any help! I'll really appreciate any help, because there is not much info on swapping AEL.

Attached file for the wiring diagram i use - says AAT wiring, but engines are basically the same. All the pinouts are the same for me, tested with multimeter.
AAT wiring.pdf