There seems to be some speculation about this subject and rightfully so. Without going into long drawn out paragraphs and would probably end up with me stepping on someones toes, I'll just give you my opinion.
Now this also greatly depends on how you plan on driving your car, (be honest with yourself) and what your desired outcome will be. Sway bars are fine tuning devices only!! Rely more on your springs, shocks and shock valving to control your vehicle's actions. The absolute largest front sway bar for a 63-82 Corvette is 1-1/8". Your 7/8 front bar is adaquate for spirited street driving, optimum for any type of road racing is the 1". Autocross applications might (a big might) use the 1-1/8".
Any 63-82 Corvette, in any type of racing application should use no sway bar in the rear. Yes you read that right, NO SWAY BAR IN THE REAR. A rear sway bar, even the coat hanger 7/16", will cause a loose condition on a high speed corner or even on a stab and go corner. This apply's only to midyears and sharks. C4's and C5's are a different breed. What you need to learn to do, is to drive your car with the gas pedal and not with the brake pedal. When this is accomplished, you will totally understand what I'm talking about. As a test, take your favorite corner with the rear bar connected and then without. You tell me what feels better. I've told this same information to racers on all types of circuits. 90% of them, that were running a rear sway bar, has called me back to thank me.
Remember there are two different types of shops, one that sells parts and one that sells performance.
Dave Tillotson
Guldstrand Motorsports