hi Steve

1560 are differents versus 750 for the gauge wheel arm. on 1560 wheel arm is weld to his axle, then axle go trought disk bearings trought a pipe, then handle arm fit with a "fork" around the flatened end of the wheel arm axle. no way to compensate wear here with splines, on750 you can

i would go to your idea to try weld a lay of (cast ?) weld on the handle arm if you know a good welder but not sure it will weaken the arm fork or not

you could also  try to level the grove by grinding or machining then use some beading(calibrated thin steel) between the axle and arm

dont you miss french wines and kitchen?