I bought my car already converted and had the diff installed last year. The flange to the drive shaft might be different. But my 328 driveshaft was connected to my 4 cylinder diff so that may be the reason it had to be swapped.
The writeup about my car is at
http://www.318ti.org/notebook/328ti/index.html There is a good writeup about the diff conversion here
http://www.318ti.org/notebook/diff_c...ion/index.html Another cool thing is the M-Coupe cooling cover for the diff. Although you will need to loose the spare due to clearance issues. I keep the spare but have an air compressor in the car incase I do need it.
You will need a dealer to align the DME to the EWS, I think. J!m is much more knowledgable about this than I.
For my exhaust we finally just made an adapter for the two pipes from the cat into one. I also used a Dynomax muffler. Once I removed the POS Walker that I had installed a couple years ago, the car has been transformed.
Once you have the tranny out I'd do a short shift. I'm using a UUC and am very happy with it.