Do not the four bolts hold pulley on to the clutch and reverse sprocket is bolted to pulley so the only load on the 4 bolts is the rear chainIJ I put in updated shaft in my 62 and 72 this year,parts needed are;1 shaft,2 bearings,3 sprockets because shaft is bigger,1 star senor wheel,1 spacer,1 hub,1 keystock, 1 flatwasher and bolt from Agco.