120-240/50 uses 3 pins (H H N) and a ground collar
that's what i use on my early 53, it works fine 99% of the time.
the only time it's not enough is when i need to run the freedom 30 inverter charger and all 4 ACs and all the lights, etc... it trips the dock breaker. but for the stuff the boat came with, it's enough. just.
so, when we need to run all ACs in summertime, I just reduce the charge rate on the inverter...
my boat, like most hatts, also has a pair of 30amp inlets, selected with a rotary, although the rotary doens't look original. I know the later MYs have their rotaries on the panel by the helm and more options, including selecting port and starboard side inlets, I think. Mine doens't ... i you open the covers while the other side is connected... dont' stick your fingers in there.