What is the difference between a single wire alternator and a dual wire alternator? and what alternator should I use? The electrical system on my re-power is a very simple 1940 style. I have changed the water inlet and thermostat housing on my 4BT to a '95 Dodge 12 valve style (because it suited my radiator hose configuration better) and then I proceeded to install a '95 OEM Alternator; that's when I noticed a few new problem. First off, The alternator requires a computer assisted regulator and my vehicle was built be for computers where invented. Second, the fan belt from the 4Bt is 53" and I will need at least a 56" or 67" belt, if one is made.