I have spent some time over on
www.stovebolt.com in the "big bolts" area and there are some really knowlegable guys over there when it comes to stuff like this. My understanding is that all of the PTO units were afer market. I took a quick look over there hoping to find some info for you but only came across this one:
http://www.stovebolt.com/ubbthreads/...436#Post829436
A lot of the c40, c50, c60 and c70 trucks had PTOs on them to power dump beds. I have no idea of the value, hopefully somone else can chime in with more.
-Richard