Here are the printed parts for the B50 version of the KTM clutch
The chainwheel will have to be steel because of the closeness of the teeth to the diameter of the plates. Probably use 1045 or 1144 Stressproof which can be hardened to 52 Rc.
The chainwheel runs on a needle bearing, the drum runs on a bushing. When the clutch is lifted the drum is held against the hub by the spring force so the only load on the bushing is from the clearance in the needle bearing.
All the other parts are KTM.