Thanks Bruce, i`ve been ordering sprockets, a new 7 hp motor and other stuff for the build.
My plan is to mount one of these mowers between a couple 2x6`s in the front so it works just like pushing it.
Then i`m going to make a 8 inch wood drum for the back and chain drive that through a jack shaft to a centrifugal clutch on the motor.
Hopefully it will work.

It will have handle bars on the back and pull a single axle dolly with a seat i can ride on.