[Aussie Mike]

Just a thought but why not build it rear engine with an IRS rear suspension setup or even a DiDion rear axle setup. It looks like the boot area might be big enough. If you are using the bike engine you could use a chain and sprocket to or even a belt drive to drive the diff center.

Alternatively use the complete drive train assembly from a small front wheel drive car installed in the back. Suzuki swift or Toyota Yaris or something like that. That way you would also have reverse gear and an option for an auto trans.

I've often thought the drive train out of a Golf GTI would be a weapon in a mid mounted installation. DSG gearbox makes for lightning quick changes and paddle shift and no need for complex gear linkages or a clutch pedal. All of the pluses of a manual box and the convenience of an auto. I've got 2 VW's with DSG boxes and they are great fun. It even blips the throttle on down shifts and you have engine braking.

Cheers