I wouldn't go past a 255 to keep the tire from being pinched but you'd be best to stick to a 245 sized tire to be safe and get the best performance out them.
FRPP HotRods Cams / American Racing Headers Long Tubes with catted X / Stang-Hi dyno tune
Saleen wheels / Steeda CAI / Corsa Xtremes, K Springs, Koni STR.Ts, UMI lca relo. Brackets/r lwr ctrl arms UMI adj. panhard bar / Camber plates / SR Strut Tower Brace.