Updated: Oct 26, 2014 Added more 1st gen pics
AC A212CW Air Filter
The originals had a square mesh then later GM came out with the diamond mesh as shown here which I still own.
They call this a 14" x 3" filter even though it's not really 14" in diameter.
Compare 14" x 3" NAPA Gold 2095 vs ACDelco A212CW
AC Delco A212CW in a GM open element breather
Base is 14-3/16 in dia.
Lid is 14-1/4" in dia