Was recently at a car show in Grand Rapids Minnesota and a vendor in the flea market area had a few old cat manuals and tucked in with them was a book published in 1971. It's titled Seventy Years Down the Road written by Herbert Reese Sr. It's a look back at his work life using machines from hit and miss gas engines, logging equipment, cranes shovels and trucks. He built roads in Northern Minnesota near Greebush into the Dakotas and Canada.  Some of his equipment included 2 Cat RD8s which he bought new. S/n 1H519 and 1H522. Also a Cat #48 elevating grader. It's unclear what happened to the cats but he states that the WWII War Production Board requisitioned the machines to build ordinance plants. It would be something if these RD8s were still intact somewhere. 

sounds like a good read.