The Holley model 4165 is a spreadbore, mechanical secondary (double pumper) carburetor. The spreadbore flange has 4.25 X 5.62 inch bolt centers and larger secondary throttle plates than the primary.
Model 4175 carburetors are also spreadbore, but use a single accelerator pump and vacuum operated secondaries.
Carburetor numbers are stamped on the front of the choke tower in these models. How to find Holley carburetor list numbers