I am new to a lot of things with this being my first build so my question may seem easy to some people. I have a 72 Dart Swinger that is a factory A/C car. The compressor uses 2 V belts but some newer cars use just one. I am putting the March Performance V belt pulleys on my 360 but the pulley for the alternator is a one V groove pulley. So that is why I am wanting to know the use of two belts on the compressor.