Splashoil - the true GMC engines used mostly Zenith and Stromberg carbs, and excellent carbs they are.

Rusty46 - most of the aftermarket Carters have the number stamped (not raised) on the center section.

Pete - it is possible you have a problem with idle adjustment. Give me a call during normal business hours to discuss.

Jon.

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop