I'm not sure about the old glowheads. If they are, in fact, 1.5v, then you can use C or D cells. I seem to recall seeing old glowheads that were a higher voltage though. You can try hooking up a 1.5v battery and seeing if it works, or looking to see if you have a bright glow or not. (heck, if they are that old, you should check to make sure they still light anyway.)

I think (not totally sure though) that a 1.5v glow plus pulls about 2amps normally.