help pick 17"ers on a 70 Swinger

I don't know what kind of backspacing the RMS needs. But I know most people who run 17" wheels run a 245/45/17 or a 245/40/18 for 18" wheels. That's going to get you as tall as a tire as you're going to get. With some minor modifications you can fit a 275/40/17 or 275/35/18 tires all the way around with the 17" and 18" wheel respectively. They are just as tall as the 245 series tires.

Here are some pictures...

I believe these are Mustang wheels:


These are 18" wheels, 245/40/18x8 in the front and 275/35/18x9 in the back. I believe all he did was roll the fenders or cut the rear quarter panel wheel lip: