G.M.C. used the following Zenith type 228 carbs on the 270:

9778, 10528, 10557, 10829, 10899, 11442, 11658, 11852, 11963, 11965, 11967, 12027, 12057, 12058, 12059, and 12496

I.H.C. had engines of displacement 264, 269, and 282 that used single barrel Holley carbs. Not personally a big fan of Holleys, but some folks like them.

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