Alternator Amperage Question

IF the wiring is "as" absolutely like new condition, you will probably get by OK with a 60A so long as you don't have a lot of "big" accessories like big headlights fans, etc.

A 45A would be fine.

REGARDLESS you should take a look at the wiring. Read that MAD article fully. It gives a very very good overview of all of this. The number one big thing is to check the bulkhead connector. Pull the connector sections apart and clean, inspect, repair them at minimum.

Many of these cars have voltage drop issues in the harness due to bad connections and switches. My own 67 had 1.5V drop from the battery to the ignition system. This causes overcharging