lcfman - A little searching through Chevy Parts books shows the original air reservoir tanks where listed as GM# 2463013 and where used in 1965-73 Chevy trucks equipped with air tanks. Some single tank and some double tank systems depending on the model number. There is also a later 1984 Chevy School Bus catalog that lists the same part number in use on school buses at least up through 1983. Sounds like lots of possible source trucks to try and find a suitable original tank for your truck.
Here's one source that lists a lot of C50/C60 series trucks over this time period and might have what you are looking for.
C&H Truck Parts is located in Sioux City, NE.
