yes its a direct fit, all the 6cly motors in the E36 era were the same size, motor mounts are all in the same spot etc, no suspension changes required for a straight 6 cly swap. if your car is OBD1 and the 328 is obviously OBD2 than you would need some programing done to make it work on OBD1, including EWS bypassed.
there's a modification that must be done to the S50 crank in order to fit an M50 block. the easiest way to go is to get the kit from zionsville. you really only need the crank and rods so you could always sell the 2.8l pistons. i would rather keep the M50 pistons because they are already broken in to that engine.
The AutoGuide.com network consists of the largest network of enthusiast-owned enthusiast-operated automotive communities.
AutoGuide.com provides the latest car reviews, auto show coverage, new car prices, and automotive news. The AutoGuide network operates more than 100 automotive forums where our users consult peers for shopping information and advice, and share opinions as a community.