I'm going with either the HT440 (my first choice) or HT600. I actually found a broken piece of one in my FHP car, and it's definitely the lighter-colored case. I worked with a bunch of the guys, also, and I remember the portables being that color (at least in my area).
Here is a website with some good pictures of old Motorola portables:
http://metrocommnj.tripod.com/id9.html
I'll look through some of the "Real Stories" footage to see if I can confirm it (should be easy since the antennas are on opposite sides).