Take a look at
EAA Chapters - Electric Auto Association to see if there is an EAA club near you.
To test a motor a 12v battery should be plenty, I agree that golf cart motors are not good for vehicles that weigh over 1,000 pounds or that you want to go over 35mph, altho the c-cars are not really supped up golf carts... at least I haven't been able to find any golf cart parts that work on either the citi-car or commuti-car, but they do resemble golf cart parts and are golf cart size EV's.
If you do need to drive 50 miles at a time, buy a Diesel or a Honda Insight, diesels are good for long distance driving, EV's are good for those trips that gas engine vehicles don't work well for.