From E30 Zone Wiki
The E36 is the third edition of BMW's 3 series cars, following the E21 and E30. It was produced from 1991 to 1998, when it was replaced by the E46. It contributed a large part of its drivetrain to the Z3.
These are the parts can be bolted directly to the E30 with little or no modification. They are considered an upgrade for either strength, performance or cost reasons. Anything not on this list is either directly incompatible or requires significant fabrication to fit.
Main article: Engine Swaps
NOTE: The sump on all E36 engines must be changed to an E30-compatible equivalent. This is because the location of the oil pan interferes with the E30 subframe
Gearboxes can be fitted with their matching engines, but E36 gearboxes sit at a different angle to their E30 counterparts. This means that modifications must be made to the gearbox mount and shifter mechanism
The steering rack is one of the standard upgrades for the E30, thanks to its faster turn rate. However, custom piping will be needed to overcome the differences in power steering plumbing, as well as components from the E34 system.
Due to the age of E36 parts now, it is more desirable to use the steering rack from the E46.
Specifically from the 318 Compact, the rear beam including trailing arms is a direct bolt-on replacement for the E30 unit, and is commonly used when converting to a 5-bolt hub.
Front wishbones fit, but are inferior to E30 ones. All other suspension components are incompatible, unless specifically E36 M3 Evo parts are used.