If you have a place to put it, you may consider a built in single room forced air heater or two. These can be thermostatically controlled either on the device or remotely. I have considered this myself, but the 2 portable ones we already own just keep on ticking.
'04 GMC Sierra 2500HD, CCSB, D/A, MaxBrake, B&W Companion, Retrax Pro, AR Power Steps
2013 Rockwood 8289WS w/Diamond pkg
1969 Camaro RS/SS Convertible
Dad's old 1968 Empi Imp (recently recovered from under 21 years worth of boxes/dust)