There were hundreds if not thousands of them hauling grain and pulling end dumps in Texas in the 60's. The 409 was the preferred engine and they were usually run til the engine blew and a new GM long block installed. When the cab got too worn out for another engine, they were usually parked and later crushed. Very few of them survived. Here is one that is for sale that looks pretty much like what they looked like back in the 60's when guys were bouncing pills off the windshield and running 3 loads a week of grain from the Texas Panhandle to the Gulf ports.

http://www.desertclassics.com/DC10/Chev64SP80tr.html

When gas went from 20¢ to 50¢ a gallon in 1973, just about all the gas burners that were still running were parked.