[chuckm]

Here's an idea for recovering some exhaust heat: Wrap your exhaust headers in 1/2 or 5/8" copper tube. Run one end back up to a point behind the radiator, bell it out and put a fan sucking air through the radiator and pushing it through the tube. The other end of the pipe could be run to a low point in the coolant reservoir and through a bubbler. Put insulation around the pipe running to the reservoir. Once your coolant temp is up, turn off the fan.
Probably not very efficient, but relatively simple.
I suppose you could even pump the coolant from the reservoir and back again. The problem of coolant remaining in the tube could be resolved by opening an air valve on either the suction or discharge and letting the fluid siphon back down into the reservoir.