E30 M3 was built in the same factory as other E30s, but not on the same production line. The workers that built the M3 were carefully selected from amongst the factory staff to be the best. When they couldn't keep up with demand they had other workers make their coffee and bring it to them on the production line, so they could keep going and not have to stop for a break!!
Quite right Josh, there were differences between the road car and race cars in the suspension department (greater variation as the years went on - mainly due to the development of the race set-ups), but there are also big differences between any other E30 and the M3 suspension. Changes were allowed between the production vehicles and race vehicles in certain areas but they had to be pretty much the same in others - body shape / size, engine configuration etc. Hence the need for an M3 road car to base the race vehicles on, although BMW really did it the other way around - working out what they needed in the race car, and then building a production version that had what they needed.
And there is still a huge difference between an "M" and a car with TradeMe M badges!!!