The Schumacher catalogue uses sizes such as "20x15" (the stock part), and "8x10", "3x20". The numbers strike me as a bit inconsistent. Edit: maybe 1st number is mm width, 2nd is mm sidewall height?
Smaller overall OD would be fine - would give more torque [useful] but lower top speed [not needed]. Whereas larger OD would strain tranny and engine more anyway? Same OD would be good compromise - don't want to lose too much ground clearance.
I see from manual that the wheels have dogs to the driveshaft. Normal, no doubt, but need the correct hub/dog size?
Short version of a long waffle ....

[Yes, yes, I haven't got the thing running yet
