68 Barracuda tire sizes

I run 295/50-15s in the stock rear tubs. I have fit 325/50-15s in those same tubs.(68S). So the rear will accept almost anything, with careful set-up.
I have run 245/50-15s on 15 X 8 steelies up front with careful backspace selection, and some minor trimming at the front lower corner of the wheelhouse to the fender.That tire calculates to 24.6 diameter.I currently am running 235/60-14s@ 25.1"@ 7"rims.I am lowered, and trimmed. Your tire calculates to 26.4. If you fit it on a 6 inch rim, and tuck it in as far as it will go without hitting the balljoint or frame rail and your ride height has not been lowered, you might not have to trim the fender.Typically though, expect to trim that corner. Dont forget to allow some extra clearance for brake-dive. Forward motion cuts the tire, reverse folds the sheet metal up and tears the paint off at the fold. Dont ask me how I know. Trimming to me was no big deal. Snip, snip, hello cornering power. Just be sure to seal the cut edge to prevent water infiltration and subsequent de-lamination of the paint and then rust.