i converted my foot start 54 over to 12 volt w/ a one wire altenator and all i had to do was change the bulbs, heater motor etc and add resister for gas gauge. that motor bit the dust and i replaced it with one from a 62 chevy (235). In order to keep the foot start i had to use the fly wheel from the 54 as mentioned above.

54 3100 w/62 235 "Yosemite Sam"
Born a Jay Hawk, raised an Okie and resurrected in Texas!http://community.webshots.com/user/djed50