850 heads

I have herd from numerious accounts that the M70 that the 850 uses is just like two M20s together dose that mean they use the same heads i know the 850 has 2 valves per cylender so only one cam each side but my underline question is, are the heads the same or are there major differneces and am i just being a moron lol

Heads are identical. They are arranged so that depending on which side of the motor they are bolted to, they have a front and a rear cover that is interchangable.
The intake runners are also interchangeable left to right.
The problem with trying to bolt up "opther" heads from the BMW catalog is that while one side might work, the oil and coolant journals on the other one will be backwards....