check your local craigslist for a whole bike. Considering you can get an early model for about the same price as an engine it may be worth just getting one that way and transferring your farkles and body work over if you toasted the motor.
Also since most people don't ride much those usually have low miles but rough exteriors, I just saw a few 86 models sell for around the $500 mark, the bodies looked terrible but the bikes had maybe 20k miles on em.
Sell the extras that some people need like mirrors, seats, windshields and you may actually end up getting the motor for free.