They are not 100% the same....Just did this swap, timing case is different, oil pan is different and the e36 oil lower oil pan will not clear the e30 steering rack, intake manifold is different (it has DISA, e30 does not, so e30 ECU does not), and CPS placement is a little different. Overall very easily swappable just take a few things from you e30 M42 and move them over and you should be good to go!