I am currently struggling to mount 295-15 on the rear with 10 inch rim with 4.5 inch backspacing.
works ok but outside of tire is flush to outside of fender, so fender has to ride above tire.
If I can move the wheel in 2 inches (must relocate springs to do so) then the tire will just fit inside the wheel well with about 1/2 inch to clear on outside and inside.
The wheels I choose (centerline autodrag 3) are not made with 6.5 inches backspacing so I have to narrow the rear end. If you choose a wheel that has 6.5 inches backspacing, you will just have to relocate the spings inboard 2 or 3 inches, but you wont have to narrow the rear end.