Jamie, I know there are formulas for everything, and have no doubt you can use them, as can I ..... lighting is rated in watts, radio audio output is rated in watts, motors, as well as the vacuum tubes / transistors and transformers in radios are rated by voltage and amp draw - wire is rated by ampacity ..... I told you above what the fuse ratings were, and that gives you what I thought you were looking for, the max possible draw for those circuits to size the wires and an alternator [rated in amps], I hope you're not looking for the absolute least you can get by on, anything electrical needs a margin of safety .... for what GM has to say about the factory radio see here, for a deluxe heater see here, for the wiper motor see a '57 shop manual [not one online]

Bill

Moved over to the Passing Lane

"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir
"When we tug a single thing on an old truck, we find it falls off" ~ me
Some TF series details & TF heater pics