Bolt Diameter Differences

I've got a set of Rallye rims that I want to place on my '70 and they have the 5 x 4.5 bolt pattern.
If- and I say if, because I'm not with the vehicle currently- the bolt pattern is different on the existing wheels on the car, what are my options?
If- and I say if, because I'm not with the vehicle currently- the bolt pattern is different on the existing wheels on the car, what are my options?