I use this 1964 Ford 42 amp alternator with an external regulator. It is the OEM type for a 289 Car, although outdated by todays standards it has served me well for many years and therefore I chose to continue using it when I rewired the car last Winter. I have the typical lights, Spal fan, mechanical gauges with lights in them, MSD-6T ignition, turn signals, brake lights and 3 relays used throughout the system. The only time I had any problems was when I chose to run a reduced diameter crank pulley and in town it did not develop enough current due to reduced RPM. I just think the high amperage units are overkill if you do not have accesories that require it.
Rick