Plymouth Duster 1973 small block wheels

Are these wheels you already have? Or are you trying to determine the offset you need to get those wheels to fit on your car?

If it's the latter, we're going to need a lot more information. Are those 15x8" and 15x10"? What size tires do you want to run on those? What brakes and bolt pattern does your car have? What rear axle is in the car? Is the suspension stock?