holy crap, $2500 for M-system rims! Crazy....
(they have the same offset as Style 5's, too)
Also, I think 4:10 diff ratio is too high with a manual trans. would be something like 4000rpm at 75mph.. It would be ok if you are sticking with the auto...
A wiring harness is an easy find, any e36 m50tu will work, ie: 93-95 Vanos engines... usually around $100 at any local salvage yard. pretty certain that an e34 m50tu harness is different.