I found a 12 volt electric heater, NIB at the L.A. Roadster Show
swap meet....twenty bucks. I haven't installed it yet, it's 105 degrees out here in Cal. right now. But the cool thing is, it will make heat as soon as you throw the switch. And the other cool thing is, I already put the switch and wiring in the dash for a regular heater fan.

Life is good,
Daver.