The cynic in me suspects that DR (a marketing company) uses enough B&S motors that DR can get B&S to make them to some non-standard spec so DR captures the parts market or can sell more machines when critical parts are unavailable. Have you considered repairing the engine? Internet small engine parts stores can be helpful in finding parts.
I’ll have to take the drive belt and centrifugal clutch off and see what I come up with an actual measurement . Moss road and all sent me some good info . I could have sworn it was a 3/4 shaft till I got everyone’s input. I’ve spent a ton of time online searching and you guys got me a lot further in just an afternoon.