Wheel/Tire Clearance Issues

[damnyankee36]

On my bagged 66, I decided to go with Boss 304 wheels, 20x8.5, 5 1/4" backspace. I plan on mounting 255/35-20's. This is my first attempt at big wheels and a bagged truck.

I have discovered that the rear wheelwells are about 10 1/2" wide and the tires are about 10", not much wiggle room. The tires rub the inner part of the wheel well when dumped. It's a little worse on the passenger side because the way the rearend moves to the left when lowered.

I think I can cut away about 1 1/2" of the portion of the wheel well that bolts to the bedside and also cut the bedside in the same area to gain clearance above the tire. (See pics) BTW, the tire that's mounted now is a 255/45, about 2" taller than what I plan to use.

With the wheel well cut, I figure I'll have lots of room to move the wheel out as the tire can now move under the part I cut.

Now, the only way I can see to do this easily is to install a 1/2" wheel spacer along with longer studs.

Is this problem something common? What has everyone else done? I figured the 304's were a common offset that would work on just about any truck since there wasn't another offset to choose from.