225/60/15 is probably the biggest you can go up front, 255/60/15 out back. A 275/60/15 will fit most Barracuda’s in the back in stock form, but it’s pretty tight and that tire should be on a 15x8”. On some cars it could take some fender rolling, or a small spacer to get them off the springs depending on which rear axle you have, because the 7.25 and 8 3/4” rear axles are not the same width.