Looking for freewheel crankset that will fit Schwinn etc.

[popcornsutton]

I want to build a setup like the one in the pic I screen captured from Youtube. But instead of cutting off the pedals, I'd prefer to use a freewheel so I can keep the pedal power. I have a 97cc 4 stroke engine that I removed from a brand new Doodlebug mini-bike, which is a lightweight engine and already has a clutch that uses #35 chain. I have a new 72 tooth #35 go-kart sprocket that I would like to attach to the freewheel's sprocket. All of the freewheels I've seen for the gear shift kits have the sprocket on the right side. I don't plan to use a jackshaft to move the drive to the right side or I could just use one of those freewheels. Does anyone know of a freewheel crank where the sprocket is on the left side or does this even exist? I'd like one to fit the standard size bottom bracket like on a cruiser bike Schwinn etc. If I absolutely have to, I'll just go with what I have without a freewheel and just cut off the pedals and have a motorbike. Having the drive and driven sprocket on the left may not be possible without a jackshaft.

YouTube - 10-Speed Bike with a 5.5hp motor!