Since we went with a staggered fitment with the FR500-style wheels, we did the same with the tires and ordered 265/35/18s for the front and 275/35/18 for the rear. Sure, it is a low sidewall ratio, but if we put too tall of a tire on the wheel, it just wouldn't look at home in the tight Fox-body wheelwell.
Once the tires were mounted, we were extremely pleased with the sidewall height. We probably could have gone a little narrower with the front tires to tuck them under the fender a bit more, but they are ideally sized for the 9-inch rim, so it's not much of a concern at all. Prices for the RT-615s vary with size and dealer, and our test subjects came in around $230 each.
Next month, we plan to have the front wheel issue worked out, but more importantly, we're meeting up with Astro Performance who is going to build us one killer transmission for Stolen Goods. In the meantime, check out the captions to see just how easy it is to hook up your Fox body with killer brakes and a hot wheel/tire combination.