Alternator Recommendation

I need some alternator help.

I'm building my Scamp with lots of modern ammenities: AC, power windows, good stereo, efi, electric fuel and water pumps, etc. I know that I'll need a more powerful alternator than the stock 60 amp job. Here are my questions:

1. How big do I need to go? I think 90 amp will still be too small, so I was thinking of 120 amp. Comments?

2. What's the general consensus on 1-wire alternators?

3. I know its blasphemy, but has anyone tried a GM or GM-style aftermarket alternator? Lots more choices, including smaller and lighter. Of course, custom brackets would be required.

Thoughts and questions are welcome.