Here's what Mark Hamilton -- from www.MadElectrical.com -- recommends:

"for 63amp (10SI) models, ask for an alternator for a ’78 Camaro (with air cond.)

for 94amp (12SI) models, ask for an alternator for an ’84 Camaro, 305G engine, 94amp Alt"

I went with the 94 amp (12si).

~~ Alan Horvath
1954 Chevy Pickup
Singing his praises in the
Passing Lane