[bobcowan]

Depends on what electrical items you'll be running. I have the standard items on my car: Lights, wipers, EFI, high powered ignition, fan. Nothing fancy, no stereo, no LED's. I use a standard '70 Mustang 65A alternater with no problems. Cheap, lifetime warrenty, easy to find a replacement.

The alternater will only produce as many amps as is needed. If you install a 200A unit, but only need 50A, that's what it will produce. Bigger units are expensive, heavy, and have more drag.

Look at all your electrical items. Add up the amp draw from each one, and see what your total draw would be if they were all running at the same time. Then add a small amount for a safety facter - theory and fact often do not corrospond.