255x60 is the largest size recommended by tire mfgs for a 7" rim.
I know people run 275x60 but do they know more than the mfgs? I doubt it.

You'll have to run a minimum 1" spacer, 1.25" is better, on the rear for the tires inside sidewall to clear the leaf spring. A 1" spacer will mean you will have to install 1" longer wheel studs. That much spacer is a Mickey Mouse way to make a wheel fit.

Pass on the wheels, they aren't worth the hassle to make them fit. I wouldn't do it even if they were free.