Jimmy, the max front tire size I found usable was 245-50 (or better- 245-40), which fit well on 8" Campys and clear -barely- the outer fenders. With a few strategically placed dents here and there, they also clear the inner fenders, the windshield wiper shield and the left cowl drain-pipe. This mostly happens in full-lock turns with two people aboard. Tires that size have been on the front of our car for some 20 yrs of street use including track days and autocrossing.
This is with the factory spring spacers removed, front fender lips rolled the max, a 2 degree nose lowering and with -4 degrees of caster. Extra caster pulls the wheels back toward the cabin, making contact with things that formerly had plenty of clearance in turns- like front brake hose routings and the wiper shield. Radical lowering does the same.
Most tire clearance problems on our '72 'L' were on the left side, as many unmolested Pantera front clips seem to be slightly asymmetric from the factory. I suspect multiple factory weld-jigs were used to complete the shells and were not quite identical, or maybe the L models got a second, asymmetric jig. Avon and Hoosier sell usable street-DOT 245-40 x 15s.