My suggestion would be to find something like this...http://www.ebay.com/itm/DURA-HEAT-DFA210CV-210-000-BTU-KEROSENE-PORTABLE-FORCED-AIR-COMM-TORPEDO-HEATER-/360414118301#vi-contentWhen I was rebuilding my motor several years back in the winter in my dad's friends garage he had a similar salamander/torpedo heater that he ran with a thermostat and it would kick on/off as needed. It worked very nicely.
I contributed to the Wiki.