My friend over revved his m44 on the downshift (a lot) causing the piston to come through the block so it was time to fit a 328i engine. pretty straight forward to do. I made up solid engine mounts as the car has an impreza steering rack and the standard engine mounts no longer fit.
It runs really well and sounds fantastic. He is very pleased with it and is a lot more gentle on the downshift
https://youtu.be/-l2C0egaIlk https://youtu.be/EZki0P0dBds