Bob,
I like the 12 volt idea but what are you going to do with all of those extra amps (have you got some real loud music planned?)? I hate the look of an alternator (maybe that is just me, definitely not 1930's era). The really get that many amps the fan belt must be tight and that is hard on the water pump. Since you are 12 volts check out the "Brite" bulbs from Ron Francis Wire Works,
https://www.ronfrancis.com/prodinfo.asp?number=B%2D1125, (800) 292-1940. I have these bulbs in my '32 roadster and am very happy with them. When working with the radiator and shell remember that the radiator cap is in a different location between 1931 and 1932. I solved the problem on my '32 by using a walker radiator designed for a shaved '32 shell (are you going to shave yours?) and attaching a dummy cap to the shell with a strap from the bottom. The real radiator cap is pressurized and located under the hood. I don't like the look of an electric fan (definitely not 1930's era), what about a polished reproduction aluminum fan? Why upgrade to an electric coolant pump (definitely not 1930's era), the stock type should be fine? I think I would go with 3.54 gears in the rear end but it depends on how you plan to drive it.
Charlie Stephens