1974 Dart Wheel Size ?

I need help finding out the size of my wheels. I got a 74 Dart swinger with drums all around with a 7 1/4 rear. I know they are 14 in rims but what about the bolt pattern. I got a chance to buy the 14 by 5.5 rallys and I THINK mine are stock 4 or 4.5. How easy is it to convert for larger wheels? I plan on getting a bigger rear and a front disk conversion and want to know if it is worth getting ralls now if conversion parts are hard to come by. Thanks :coffee2: