E30 M3 have stiffer and more aerodynamic body and the M3 also have wider and taller wheels and tires, but the 2 cars have the same hood and sunroof, BMW E30 M3 got its front brake calipers from the BMW 5 Series (E28), you should also know that the E30 M3 have 265/5 5 speed gear box and its rear differential have different final drive ratio and 25% lockup.

Engines different between BMW E30 M3 and BMW E30..