Unless you have an amp, or a large electric fan (as in my case), you don't need a bigger alternator. I run a Taurus fan, and it killed my alternator in a few weeks. But otherwise, a standard alternator will do you just fine.
75 Pontiac Astre GT: 406SBC/TH350, roll bar, S10 goodies, down to 11.47 so far, more to come later.
I put an alternator on my 72 GT couple weeks ago.Parts store didnt have one for Vega bought one for chevy pickup bolted right on and same amp [63].Was 24.99 at Autozone.
NAPA part # 213-4011 should work. Take your old one to be sure, it may be clocked different. You'll need a core anyway. They should also have part # 213-4011B which is clocked different that the 213-4011. They should be about $25-30.