Great looking truck Bill!
While my initial thought is that Bill is right, this is a "home made" fire truck, it should be noted that the military had more than one type of fire truck based on the 1 1/2 ton chassis, and I definately agree the truck found is not like Bill's.
It may be a modified CCKW (what size engine does it have, and/or what shift pattern?), or it could perhaps be one of the other styles 1 1/2 Chevy, or it could indeed be a civy conversion. The pix posted is too small for my tired eyes to see the level of detail I'd like to. There is a super-nice guy in Hawaii - Jim Davis - who has done a lot of research in WWII fire apparatus and who has a nice website devoted to same. Worth checking out. Most of my research has been into 6x6 fire trucks (surprise, surprise), but I've come across a few pix of Chevys which I'll post below. Notice, I do not own the copyright to most of these photos (which are primarily from a private collection), I have permission to post them, but please don't repost these elsewhere.
Regards,
David