Sorry about the late reply, just got back into town.
I've had a '73, '81 and now own a '72 and I put 255/60/15 BFG on the fronts and put 275/60/15 BFG on the back.
Only on the '72 did I have any clearance issues with the exhaust, and since I was installing a 2.5" exhaut system my vette guy took care of it.
The '81, I'll admit was close to the rotors but still tolerable.
I restored my '72 and plan to be buried in it so I wax it every other sunday and put it back in the garage. Even though I put in a 385 Fastburn crate engine, I pretty much baby it...but that's me.
Take it easy and have fun.

save the wave,
Mark