Or my favorite option when it comes to older cars with generators!
http://www.powermastermotorsports.com/powergen.html
Ive installed a few of them in customers cars and to me its the best of both worlds. Outside its a old school looking generator case, inside is a modern internally regulated alternator. Simple hook up and can even control the factory charge lights.
Yes, you can find alternator replacements cheaper and fab up brackets and make it work, but IMO for the simplest and most OEM look (If that matters) powermaster is hard to beat.
If your not into going that route, the others all have excellent points.