The post-war BMWs had alu helical cam gears till 1969 that were matched to each engine case in paired sets for minimum backlash, cases were marked for easy ordering of spares, like "-2" or "+3" according to machining tolerances in the cases. Horex post-war had helical alu cam gears as well, there were never dramatic failures with them, just slow wear with high mileage. I think the straight cut gears on Vincent engines will not do acceptable mileages when having alu instead of steel. You would have to fabricate helical types for better operation.
Ford V 6 from late sixties till late eighties had helical tufnol cam gears but these had really decent sizes compared to the tiny gear module in our bikes.
Vic
BMW alu cam gear top, behind disc breather, oil pump bottom :
Horex 400 alu cam gear, home made experimental camshaft :