I would use a set of valves so I could control where my coolant is flowing in case I
just wanted cab heat or just bed heat, either manual or vac controlled valves. A old
street bike radiator or even an a heater plenum out of a small car and leave it together
with the fan and everything enclosed in a plastic plenum(match the sqft heated space)
A remote starter would be a good thing to have and tie it in to a thermostat so when
hit a certain temp it would start up and reheat the system. A small auxillary electric
water pump on a 555 timer circuit to circulate the water every 5 minutes for say 2 min
to get some of the heated and trapped water out of the block and into the bed.
http://store.summitracing.com/partde...5&autoview=sku
http://store.summitracing.com/egnsea...+115&x=22&y=13
I would put an extra battery in case the water pump sucked down the juice(5amps)
sitting there for a long time, At least a voltmeter in the bed so you know the level.