You can run a V8 on 6-volt and get along fine, Henry F*^# did it from 1932 on. You just need to do a little preperation and get your ducks in a row. You need to have the proper size battery cables I gauge works best, the proper ignition coil an internal resisted coil work best. The points and condenser and everything inside of the distributor stay the same regardless. You will need a 6 volt starter, and a 6 volt alternator charging system works the best. Remember there were straight eight Pontiacs and Rocket 88's that ran on 6-volts in the early years. Look at the tech tips page on my web site for more help..www.fifthaveinternetgarage.com
Thanks Randy