Good day!!
Ummmmmm, out of curiosity, why not just buy a factory manual and call it a day... You probably would spend more in the conversion than just getting one already done...
I converted a 4.4L V8 into a RWD 6-speed manual only because BMW didn't make one... But I used a good number of OEM 3.0L manual trans parts...
However, to actually answer your question... You need to redo the starter circuit... The manual version does not have the auto start feature... There is a clutch disable and cruise cut-off... ignition switch will need a wire swapped to handle the starter circuit current... If you look up my V8 conversion, I would imagine the wiring I did won't be too far off from what you need to do, mainly since I pretty much copied what a factory 3.0L manual wiring looks like...
https://xoutpost.com/bmw-sav-forums/...t-swap-13.html
Post number 124 is the break-down of the wiring changes I needed to make... You may need a lot less than I had...
Hope this helps...
Cheers!!