There should be a round tag about the size of a dime riveted to the body of the carburetor (if it is a downdraft, probably on the airhorn).
There should be two sets of numbers going around in two circles on the tag.
The outer number is the GMC number which is not as useful as the inner (Zenith) number.
The Zenith number will generally be 4 or 5 digits possibly but not always followed by a letter. The number may or may not be preceded by an O
Examples:
O-9866
O-9866A
9866
9866A
O-12345
O-12345C
12345
12345C
Watch the letters. A's look like 4's; C's look like zeros's.
A good idea to take a pencil eraser to the tag, and then observe with a strong light, a good magnifying glass and a pair of "young eyes"
.
Wish I still had the young eyes.
Jon.
