I will be changing from an original 40amp 6v generator to a higher amperage 6v alternator (1 wire) in my 1954 Suburban. I have used a 60 amp 12v 1-wire alternator through the original ammeter (years ago - no problems)
There was a 55amp optional 6v generator that year.
How high an amperage (at 6v) can pass through the original ammeter with hurting it? This 6v alternator may produce max 70-75 amps, with 60 amps at idle.