Virtually all built-in-Detroit cars (trucks too) have different wheelwell dimensions from one side of the car to the other. Our late-model F-body was no exception. In addition, some Chevys have staggered shocks (one ahead of the axle, one behind it). This can create some real clearance headaches. Be sure to measure both sides of the car before buying wheels and tires.
Another point of possible interference is the rear trailing arm (such as this) or, in the case of a late-model truck, the front segment of the leaf spring. Typically, GM "splayed" leaf springs and suspension members. That means they don't necessarily run straight back and forth. Usually, the springs angle out toward the rear. The same applies to late-model cars with coil springs and lower trailing arms. Because of this, some cars with large backspace dimensions might encounter interference problems with the trailing arm or spring before anything else comes in contact with the tire.
As mentioned in the text, the leading edge of the wheelwell often creates another interference point for tall rubber. In this case the leading edge of the outer wheelwell has been "pie-cut." This cosmetic surgery creates approximately 1 1/2 to 2 inches of added clearance at the front. A tall tire can easily fit in this wheelwell. If your car has the same clearance problem, you might be forced to perform external metal surgery, too.
At the back of the F-car, the same clearance dilemma entered the picture. This wheelwell segment hasn't been cut yet (in this case, it's a plastic fascia panel). As you can see, the clearance is much tighter here than in the front. What's the solution? We'll cut and paste the plastic (in this case), then stitch it back together. The same process can be done to metal. The text offers some very basic info on the process.
Once you have your new wheels and tires, test fit them (sometimes it's good to test the wheels before the tires are mounted). What you're looking at is a 15X10-inch Monocoque race wheel stuffed into a stock-width, late-model wheelwell. Keep in mind that the application called for a 9-inch wide slick. As a result, the tread width of the tire is actually a bit narrower than the tire bulge (this is a common Stock Eliminator racer trick, and it also applies to most weekend warriors as well).
A bird's eye view shows that the tire bulge is actually inside of the wheelwell on the top. It's close, but it does fit. Remember to check the clearance numbers again with the unmounted wheel. It's possible to return the wheel at this point if you screwed up. Once the tire is mounted, the wheels are probably yours.
This view shows the rear. Since the car was under construction, we blocked everything up to ride height so as to double check all of our measurements (which we took a long time ago). It's not a fancy process, but it works. Copy the idea. It works just as well on other under-construction late-models, no matter what make. As you can see, the tires are tucked up inside the original wheelwells, and yes, these slicks are much larger than the original factory rubber (especially in terms of overall diameter).