you have to remember that fire truck builders often took a commercial chevy truck and modified it to meet their buyers order. So any truck may have options that wouldn't be found on a "standard" chevy truck. Example Oren(the folks that built my rig) took a standard 1951 green 2 ton 6400 truck cab and frame with no body and built a fire truck by painting it red and adding many of Oren's designed parts. Specificlly, the bars around the doors in an AD cab are an exclusive Oren touch and that is how one can ID an Oren from other FT builders. Other builders had their own designs off the commercial version.

So roof lights may or may not be found on your cab... it is yours so you choose! :-)