I had 295/65x15 rear and 205/70x15 on the front of my F body. That much rear tire required rolling the fender lip and clearencing the wheel well righ tin front where the rear set belt mount was located. I also had converted to a B body 8.75 housing, which is a 1/4" wider per side than teh stock F body unit. Looked like a vintage pro stock car that way.

Previously I had 28x9x15 slicks, which are pretty darn close to 275/60. Fit great with a 15x8 rim with 4.5 backspace and require no body mods to fit.

Up front I'd recommend a 235/60 instead of the 245. Easier to find and cheaper to get while only giving up 10mm in width. these would work nice with your 15x7 plan.