Oh M90, I am also in the process of fixing a M90 onto my E36 318is. I am still planning for my custom intake manifold etc.
I believe there are 3 main things you will need to look into:
1. Crank pulley. Not all engines come with serpentine pulley (esp. for crank pulley). For my case, its a V-belt pulley thus it will have to be replaced. Since power steering and alternator runs off the crank, it will have to be replaced as well.
2. Custom intake manifold. If you are going to mount the blower the same way as the DASC, you will need to fabricate an intake manifold. You will also need plumbing charger air intake, throttle body etc.
3. Piggy back or new ECU or reflash ECU. You can't use the stock ECU with stock mappings. It will have to be reflashed with tuned settings or use a piggy back like Unichip, Emanage etc.
These are optional things I am looking into as well:
1. May replace stock gasket with a cometic stainless steel gasket for security purpose.
2. If running high boost of ~10PSI, intercooler is recommend as the air coming out of the blower will become very hot.
3. Replacing the stock injectors and fuel pump with bigger ones. Currently, I am using the pink-top M3 injectors rated at 21lbs. I don't think it will be enough at high boost thus it may have to be replaced. The stock fuel pump may not supply enough fuel as well.