what amperage alt should i run?

If you plan a lot of relays (fan, headlights, fuel pump, EFI, ...) individual relays soon become a clutter. I installed a relay/fuse box in both my A's which also replaced the factory firewall starter & horn relays. In my avatar, the black box on driver's inner fender. Search for my post "Modernized ...". 67Dart273 did similar.