You should find out what you have now. Model # is on choke tower. A few common examples: 1850 600 vac, 3310 750 vac, 4776 through 4781 are dp numbers 600 to 850. If you have a 4777 650 it can be made into a 750 with one of these: http://www.summitracing.com/parts/pro-67100c