I have an 88 325is in the garage now, owned it since 2002 and have put nearly 90k miles on it.
4x100 14's are stock, non "is" cars get 14x6s, "is" models get 14x6.5 BBS basketweaves which are very light. Center bore is 57.1mm, preferred offset is +22 to +35 depending on wheel size. 4x100 Miata/Honda wheels need spacers to get the right offset.
Steering is front steer (I just went to the garage to check). Steering ratio is a bit too slow for my preference, but that is solved with E36 or Z3 racks.
"is" and "es" models have limited slip from the factory. By this time, though, so many have had them swapped in or out, but originally, that is what they came with. Mine noticeably has it, happily.
Brakes: nope, 14's are tight, no room for 13s.
Suspension: Mac struts in the front, trailing arms with separate shocks/springs in the rear.
I'm about to put mine up for sale if you are in the market, black/black 325is, excellent original paint and interior, all the wear items have been replaced, and it's a ball to drive, but I just bought another Miata and don't have room for the Miata, MGA, and E30. As great as the E30 is, I've had it so long that it is time to move on.
Chris - 2007 BABE champion, 2008 2nd place. MGA, E30, DiscoII