John,
That is a fabulous truck, sir! MACK, until recent times, (80s-ish) made their own entire fire trucks. This one was called, I think, the Model "E", which preceded the Model "L"s. I'm away from my library, but I think late '30s through 40s. Grill is original for the Model. Probably a 750 gallon-per-minute Hale pump. I think these were standard with a straight six 505 engine, which preceeded the famous 707 six. It's probably got dual ignition (two distributors ((or one dizzy & one Magneto)) and 12 spark plugs).
The pump is driven from a transfer case post-tranny, so you first put clutch in, switch from Road to Pump, then slip it into direct gear (prob. 4th), and let clutch out.
As for foam, the truck would have a 200-500 gallon "booster tank" of water. A seperate tank for foam, much less a dedicated booster tank for foam, would be highly unusual on this era rig. Foam at this time was typically used from 5-gallon buckets with an eductor in-line on the hose, or at the pump panel. Departments could have later on adapted the truck to use a seperate foam tank that was added, though most (esp. vol.) departments wouldn't go to the trouble, I think.
Somewhere, there was a builder's plate which would give the date of manufacture. Mack did make fire trucks for the Military, I think.
Anyway, that's about all I know. That, and that it would be a shame to see this truck scrapped. Mack fire trucks were among the best ever. E Models make great hobby trucks since they're a little smaller than some, easier to handle. 'Course, not NEARLY as easy to work on as a STOVEBOLT!
-Michael
