Mongo,
The truck was delivered to Boyer as a "Cab & Chassis", with a standard drive-shaft (and GM tranny, for that matter!), and was then altered by the fire truck manufacturer Boyer who installed the pump transfer case.
I've never seen a commercial chassis of that vintage that had a 3rd-party transmission in it - that's pretty cool. The Clark tranny is probably longer than the original GM 4-speed, which affects the idea of putting in a donor shaft. Not sure what the output shaft is, either, for that matter. BUT, any competent drive-shaft shop could set-up a donor shaft to drop in. The rear-end is most likely stock.
I know the guy who sold the truck here in St. Louis - been on the block for quite a while. Glad it found a home, if only to be de-firebolted. Oh well . . . can't save 'em all!
-Michael
