JIM Mc. - My guess would be the PO was a machinist or knew one. I tore up one of those castings MANY years ago. I figured My QA-36 was junk but My Cubbie dealer had five in stock. With bearings, sprocket, zerks, etc. the replacement casting cost more than I paid for the whole blower it it works!
Charlie & All - WHEEL weights....I have a set like Michael's also.... They will fit without drilling more holes. I think I've had them on every Cubbie I've had, 70, 72, 128, 982. I have a set JUST like Charlie's JD weights....but I bought Mine used in about 1970 all rusty, no paint, inch of dust from setting in a hog house for 20+ yrs for $5/pair. I spent more for the carriage bolts, washers, & nuts than I did on the weights. Not sure whole made them but it wasn't JD.