Darrell, Whatever 4BBL that you decide on will require you to rig up some sort of throttle linkage. That can be an issue.
As you have been told the 56 and earlier Ford distributors were ONLY VACUUM ignition advance and need a carb designed to work in that system.
A lot of cars only have mechanical ignition advance and that works OK. The vacuum advance is only in operation during steady throttle high manifold vacuum ( cruise ) and adds MPG on the cars whose distributors have both mechanical AND vacuum ignition advance.
All the 4BBL carbs except Holley that are double pumpers will have vacuum operated secondaries and will be user friendly. Pete