Personally, with room temps that low, I would not go with using a tank. They are generally fine if your room temp hovers around 80 degrees, but it could be risky w/ temps that low. And there is little insulation between the warm tank air and the cooler outside air, especially at the screen lid.
However, I have never experimented with heatlamps; if you can rig something that would heat the air above/around the tank, maybe that'd work; I would definately do a "dry run" and get temps right before beinging your snake into the picture! You may have to also rig something to retain humidity (plastic wrap?) so the lamp doesn't dry the tank out too much.