truck i think is most common. also used are rig, amblance, buggy, unit, bus, bamblance, ambo, vanambulance or vanbulance, and beast. in reference to the transport units/wheelchair vans - tard cart, window licker van.
in reference to a specific ambulance - either by number (the number 5 bus) or unit number (6-12-3, 3-8, 7-2); or by name - ie Christine (an old truck you had to be nice to or she wouldn't work, for ex one day the crew put her in drive to pull out of hte bay and she went backwards till they shut her off and restarted her), Banana Beast (another old truck that had a big yellow stripe down the side of it and REAL airhorns instead of just the junk ones most of hte other ambos have - also had the old cloth bench seats, etc.)......piece of s**t, and hunk of junk.