Hawk makes billet aluminum driveshaft adapters that replace the small sprocket on bike output shaft -
http://www.hawkmachine.com/Parts.htm#20They were the first maker I'm aware of, and others since have made adapters our of steel.
I have a Hawk adapter on my bike motor. The Legends car racers used the Hawk adapters toreplace the sprocket on bike motor & then bolted the driveshaft flange of the Toyota/Datsun driveshaft (oddly enough - MGB/MG Midget as well) to this & on to rear axle.
This is another style of output shaft adaptor - bolts on like the Hawk adapter does -
http://store.uslegendcars.com/site/prod ... FDCCF3BDC3http://store.uslegendcars.com/site/depa ... illnav=yesThere's even Patent from 1987 for connecting a motorcycle engine to the VW T1 transaxle...
http://www.freepatentsonline.com/4645172.pdf- a similar mount could be made using a Corvair to VW adapter plate as a starting point (I've been experimenting - I have one of these adapters laying around) >
http://images.thesamba.com/vw/classifie ... 677980.jpgbryan