Before you go and get a one wire alternator, do a bit of investigating and some trouble shooting/diagnosing first.
Where are you reading that voltage from, if its from the headlamp wiring, I'd expect it to be that low.
Also, the original alternators (if in proper working condition) when powering the original electrical demands of the 1st Gen Camaros are fine, it's the mechanical voltage regulators that fall short and usually cause the alternator to not perform at their peak ability. A solid state external voltage regulator is the only way to go for maintenance free (as far as voltage regulators go) peak charging system performance with a properly functioning 3 wire original alternator.
Take a few minutes and do some reading at the following three links:
1. ONE-WIRE compared to THREE-WIRE alternators - http://www.madelectrical.com/electri...hreewire.shtml
2. REMOTE VOLTAGE-SENSING - http://www.madelectrical.com/electri...esensing.shtml
3. BRIGHTER HEAD LIGHTS - http://www.madelectrical.com/electri...adlights.shtml
I run an original 3 wire alternator with a Wells VR715 solid state external regulator (one of the best electrical upgrades available in my opinion) and a Amico headlamp relay (the second best electrical upgrade and it could be any of the headlamp relay kits out there, I chose the Amico as it was very cost effective) and this combination works just fine. Having stated the previous, I'll add that the only real increased electrical demands of my 69 Camaro are the higher wattage headlamps and the Pertronix Ignitor III ignition system. I run a mechanical fuel pump, the original Z/28 mechanical clutch fan setup and a very small amplifier for the stereo head unit. My system puts out 14 plus volts at idle with no problem.
If you have a high electrical load thumper sound system, electric fan(s) setup for your radiator, and/or an electric fuel pump, you may need a larger alternator, but a three wire system will handle the electrical demand much, much better than a one wire system so do your homework if you go with a larger alternator before making a decision.