That's correct, stock was 14x6's, but there were a couple of optional 15x7 wheels available from BMW. They're probably still available, though not too cheap. Figure something like $1000-1100 for a set of five brand new.
The
Style 10 and the
Style 5 will both fit any e30 except the M3. You wil see a 16x7.5 inch Style 5, but that will only fit the M3's five bolt hub.