Try Shapeways.com - Specifically "Madaboutcars" he has several 1960s and 1970s vehicles that can be converted into AF ARFF Apparatus and Air Police/Security Police vehicles, like the 1966 Dodge Powerwagon. I've made 10 of these for such layouts. Watch out though, Shapeways is irrationally and criminally expensive. Until someone comes along to challenge their prices we just have to suck it in, unless you complain like I do. You can use the Gathering of Eagles movie for some great reference material and there are select images available on the web. The Aviation Megastore has O-10 and P-13 vehicles available in 1/72 scale.
There's a website for Air Force Fire equipment: http://www.firetrucks-atwar.com/af.html that has lots of references.
Oh, you can combine the Dodge Crew Cab Powerwagon with a bed cover (also found on Shapeways) and if you make your own decals you can make it look like a real alert vehicle. Mock flashing lights can be obtained from Detail Associates #2901 (round top) and #2902 (flat top) but you will have to stain them with clear red, about 2 coats and paint the bases silver or red if your photos show them that way. Hannants of England also have quite a bit of GSE like B-4 and B-5 maintenance stands made of etched metal, all in 1/72 scale, and they have generators and other stuff too. It's popular so there are a lot of items seemingly perpetually out of stock. There are a lot of scratch-building references for USAF GSE on the web, takes time to find and build. Some names you may need to know for the Crash Fire Rescue Vehicles: Marmon-Harrington; American General; American La France; and Ward La France; also White Cardox (O-6).
I hope this helps.