thanks for the comments guys

vstech, you're right about the lower rpms but that's part of the challenge. about the gasses temp, my main concern is that when you have the turbo, there's backpressure in the exhaust manifold which means lots of heat staying there, which puts your engine head and valves in risk. I agree with you about the IC, but I think that a supercharger will allow the use of a smaller one, which is specially good for the W123 little room.