Over cooling??

Hey y'all,
Anyone ever had their XJ run too cold?? I live near Toronto, Canada and we just had our first snow fall, and I can barely get the temp gauge to move... and barely any heat comes out of the heater/defrost. When I stop at a light the temp goes up slightly, but as soon as I start moving or rev the engine in neutral the temp quickly drops.
My first thought is that the thermostat is stuck open (failsafe), and that I should just replace it. Any other suggestions/ideas???
Thanks for any help.

THat is the only thing I could think of that would cause the temp to stay low all the time. I'm not sure how good the towing package cooling system works but our family had one on a Ford Ranger and you had to put cardboard infront of half the rad during the winter to keep it warm everytime the rad cycled the coolant the coolant temp would drop back down to cold. If the cooling on a towpackage XJ is anywhere similar that could be the problem.

How can I tell if I have the tow package? I mean it has a trailer hitch (not sure if its OEM), but doesnt seem to have any other auxillaiary coolers or stiffer rear springs..?
Its a 93 4 door Sport with auto and 4.0. Any way to tell by the VIN # ?
Thanks.

The thermostat is the most likely problem. It is relatively cheap and easy. They should be changed every 4-5 years anyway, especially if you don't run distilled water in the radiator.