Thanks for the info guys. Going to get the M3 tomorrow. I'm going to do a bunch of CAN logging on it then start ripping into it.
I do plan on using the whole M3 harness, just need to rearrange some tail light wires, and probably a couple other minor things but everything I've seen so far is that my 2012 135 and 2013 M3 are basically exactly the same. And yeah, all the M3 modules will come over as well, except the NFRM I think... the 135 unit has to stay because of window limit detection or something like that. They're the exactly same unit and exact same wiring pin out though.
The way I'm approaching this is basically just using the 135 shell and bolting a shortened M3 to it.
I think at this point the only real major differences that need customizing are the heat shielding, brake/fuel lines, exhaust, and driveshaft. Everything else seems like just bolting M3 stuff onto the 1 series shell, but I'm sure it won't be quite that easy. I'm not particularly worried about the air intake just yet.
I do think the oil cooler fits, but just needs trimming like a large aftermarket intercooler... we'll see. @martymil You sure the DCT cooler doesn't fit? I thought it was the same as the 1 series oil cooler. I was planning on getting a CSF unit anyway since this is going to be 99% a track car, and I think most of the coolers on my M3 are going to be destroyed. Shouldn't be an issue either way though.
Using the m3 wiring loom is the easiest way to do it but be very careful not to damage the optical wiring, that will be a nightmare, take your time with the harness.
There are going to be small differences but nothing major and if your in USA there is a number of people that already done it so if you get stuck they should be able to help you out if you ask nicely LOL.
100% the cooler does not fit but the connection is identical so all you have to do is flush out the n54 engine cooler to use as a dct cooler or get a csf n54 engine cooler and use it as a dct cooler for the s65.
The s65 engine oil cooler sits across the front of the car similar to the n54 IC but further forward, basically where the bumper bar is.
Heat shielding fits with a little trimming.
If its a track car the exhaust is easy, no noise limit so any exhaust shop will fab that up for cheap.
Thats some serious work completed, extremely clean seamless install... congratulations very nice job! Youre not joking about your coder/electronics guru Tom being the beeeeeskneeees, that is some serious magic he worked. Thanks for sharing!