Something to consider Terry. Use Bosch or other 30A common automotive type relays to handle the motor switching. You can get prewired pigtails for them with a connector on the end. Use maybe 4 of them in a stage 1, stage 2 configuration with a large wire wound resistor in series for stage 1 to limit current. Run the inexpensive relays in parallel. A couple of toggle switches to control the relays. I use 12V wiring in a few hobby systems. The cigar humidor built into a Coleman beverage cooler with freon cooling for fans and temperature control. Also use 12V fans in entertainment system amp racks, along with fan speed controllers to manage air flow.
I use the Bosch automotive relays in my nitro start cart on the Dynatron's as I've had the handle switches weld themselves together. The handle switch controls the relays, so very low current on it.