Turns out...
A Zenith 228 has a 2 1/2" hole spacing, and a 261 intake manifold has a 3" carb stud spacing. Jerry and I talked on the phone earlier, and I will weigh my options on an adapter plate, or selling the Zenith and buying a Carter that would feed enough air to my bored 261. I could slot the Zenith base holes 9/16" but I'd rather not do that...
