That's the motor, they have the same cast iron block as the '83-'91 E30 sixes, but have a twin cam head and better flow capabilities.
By memory the 83-91 SOHC is called an M20, the 91-97(ish) E36 DOHC sixes are called M52.
http://en.wikipedia.org/wiki/BMW_M20
http://www.bmwworld.com/engines/m52.htm
Like I said if you've got the cash, you could do the E36 M3 motor (think it's a S52B32 designation), but the later evolution motor in 3.2L is better.