From spanky on a different post:

6700?, Donnoman your truck looks to be a 6100, or 6400. 6700 series is a Schoolbus chassis. If "6700" is what your fender emblems say, they have been switched.

In the one vin calc I ran it in it said it was a 6100; So I suspect you are right. Searching for 6700 all I got were schoolbusses.

Taking a closer look at the truck; Neither fender fits very well so I think I can assume they came from something else.

57 Chevy 6100 Wrecker http://donovanbray.com/tag/57wrekr