http://www.cmsnl.com/kawasaki-1983-kz750-f1-ltd-shaft_model15513/partslist/19045.html
This looks interesting, factory bevel drive,
to turn a chain drive into a shaft drive. [cl
That sound is "wheels turning".
[ddev Imagine this:
Your choice of 4 cyl bike motor, cut the trans off,
turn the motor sideways. No prob so far.
Couple that Kawi' bevel drive(above) to the back of the motor,
so the output is on the left side. A sprocket on the output
would drive a chain connected to a Harley trans. (I've seen
"new" rubber mount HD trans on Ebay, with a damaged case,
for a couple hundred. The part that was damaged wasn't
necessary for a non stock application. [clCut that part off)
The input and output are on the same side of the HD trans.
That would get away from the shaft drive,
and give more options on wheels, frame stretch, etc.