so maybe we're talking the difference between gauges of the different year series, I don't find a rating shown for the 55-59 gauge anywhere [series in question here], but I know there was a 55amp HD generator available, so I'd expect the gauge should be able to handle that with a margin of safety .... and I've never seen a TF gauge peg under any conditions, although I'm sure a defective regulator could do it
but good tip on the shunt sizing for those that think it's needed, although 'upgrading' to a volt meter might be preferable
Bill