Michael,
The 7hp Briggs and the axle are probably from a rototiller or a snowblower. 5-speed+R gearbox from a lawnmower tractor and tires from my former old Volvo.
Belt drive from motor to gearbox, with tensioner acting as clutch. Motorcycle chaindrive from gearbox to input screw into the axle. Leftover cut out domes from propane tanks act as “hubs” for the rims.
@Bobmac and @KristijanL,
I agree, it’s a good charcoal candidate. We’ll see what the future brings. Screen out some fines and I can probably run from what the Mazda produces.