Crankshaft pulley

I googled this first but couldn't find what I was looking for. How many grooves does the crankshaft pulley have for ac? If I were to install a ac system on a non factory ac car do I need to convert to the dual belt set up? The car does have factory power steering. Thanks everyone. The car is a 1973 dart sport with a 318. Trying to get with the owner but with all of the tornadoes and other bad weather going on in Illinois it's making it rough. But I'm sure it will happen.