Sad to say that Sue Mitchell has passed away. She was a lovely lady and great friend of the the Model A community, and long time member of the Sonoma A's.
I've been off FB for a while but here's my take. Mount the switch in the seat riser if your A has one and switch the ground. Anything moving around under the seat will not create sparks when up against the connections. I've seen holes drilled in freshly restored firewalls and wires cobbed...
I've run a Brass Works 8 fin radiator coast to coast pulling a trailer, and to Dallas and never had to add water. Just be sure you thouroughly clean out all rust & sale from the water jackets.