Honestly your best bet would probably be a 6speed manual from a W203. i wouldn't be suprised if all the bolt patterns on the bell housing were identical and if it fit perfectly. Also I bet driveshaft may even be the same length. A 6speed C transmission with the proper clutch/flywheel setup would be able to handle the power. as far as internals i bet they are probably strong enough for 400 crank HP so for C36 application they should be perfect. also all other W203 components should swap over very easily. that is your best bet. hope that helps