I've been working on some new front brake drums for an early 70's Max II.The early Max Ii had #40 chain. I machined up some new drums and new sprockets that are splined to fit the new splined axles I made.The new sprockets are #50 chain.I made a fixture to fit inside of the drum to keep it centered with the internal spline,so it will run true after welding.Then will put it on a splined axle and turn the OD of the drum so it will be true to the 6-spline.