In a 7 the motor will be up front so that's a hell of a long chain run...
I took a gearbox sprocket from the Triumph to a machine shop who then hoofed off the teeth and machined up a noggin of steel with the same bolt pattern as the ford drive shaft UJ...the two were welded. This bolts on as per a normal sprocket then the prop just bolts to this...Don't go making a prop though as bike motors spin quite a bit.... Bailey Morris etc Reverse is a matter of a wee sprockety thing mated to same sprockety thing on whatever bike starter motor you use, some form of lifty uppy downy or pully inny outty device to engage the gears and bobs yer knobend....then it's wiring it all up so it keeps IVA bods sweet.
You will be surprised how good the reverse is even using summat like an R1 starter motor(thats what i used).

All manner of much quickness can be done, flappy paddles on the steerage down to full throttle gear changes by using elecy bits to cut the ignition just as you snatch another gear....just hang on for dear life Oh and might pay to have a slippy diff so you don't waste all that luvvly car engined whooping whoopness.

Just ask anyone with a bike engined car or look at the fizzgog of someone just driven one...........you will be hooked.