Alternator Sizing - Amp requirements

I'm trying to decide on an alternator for my big block 66 Dart project. I'm thinking a toyota Denso 90 amp should work, but what do you guys think? I'll be running an electric fuel pump, Taurus cooling fan, MSD ignition, line lock, head/tail lights, etc.

I know the right way to figure this out is to add up the amp draw and size the alternator accordingly, but how do I know how much power a particular alternator produces at idle?

Any idea if a 90 amp alternator would get it done for me? Thanks guys. This electrical stuff is like black magic to me.