[amg6975]

Yeah so yeah. You essentially need an entire M3 to do it right. It's far, far more granular than you've documented here so far. "Electronics" isn't a whole thing, you need to mix and match M3 modules and 135 modules, wires, buttons, relays, connectors, coding, etc.

To answer your questions at a high level:

-Fuel System: M3 everything except tank, including fuel pump module
-AC Compressor: M3
-Radiator: M3
-Heat Shields: Mix and match 135 and M3
-Trans Mount: M3, plug and play
-ABS/DSC: M3, including the accelerometer under the driver's seat
-Firewall Penetrations: All M3
-Pedal Box: same thing between the cars but the throttle needs to come from the M3.
-M Button, DSC button, EDC, etc: These types of things are the hard part. If you don't know the answers to these or know how to figure it out this swap is going to be very hard.

There are 100 other things you haven't though of yet. Pre planning the whole project is basically impossible, you need to get the two cars in front of you and start going through every single detail of them and figuring out how they blend together.

It's not rocket surgery, but it is A LOT of things to figure out.

I need to move my build thread over here but if you Google my username and "M1.5" I think I have the most detailed build thread on the internet so far.