Sounds to me like you need to do a tune-up, new plugs, wires, cap, rotor, double check the points and condensor (or change to an electronic setup). The glow is not normal but retarded timing could cause it, and if the plugs are worn it will change the timing. It's the little things that keep stuff going, as a fire dept you can't afford downtime on any equipment, my advice is to keep the maintenance up on ALL the vehilce in the dept. You wouldn't like it if your house burnt down because the dept was (no offense) too cheap to maintain the vehicles, plugs, wire, cap, rotor, oil filter, oil, and air filter for the truck should be under $50 total. So I cannot stress enough that you need to at least do that much...... You might also check to make sure the choke is working properly, as a lean condition can make it run hot as well, and cause serious damage to the engine.