Howdy:
All ford distributors of the Falcon era are designed for a ported vacuum source. The combination of initial advance setting and built in distributor advance are the variables that equate to performance and economy. a ported vacuum source will have little or no vacuum advance at idle, but advances as rpms increase- in varing amounts depending on distributor. A manifold vacuum source will give maximum advance at any high vacuum engine condition, such as idle and cruize. So, depending on what distributor, if you use a manifold vacuum source on a ported source distributor, you will be getting too much advance at idle and off-idle, and likely at cruize speeds.
Maniflod vacuum to a stock type distributor may be a part solution tuning carbs and timing on engines with a performance cam and/or an engine with low vacuum.
Also the Holley 1940 is a generic carb designed as a replacement carb for the stock Autolite 1100. It is a poor substitute. It should closely match your engine, trans and vehicle combination. A mismatch can be a real head ache.
More information, as Dan said, would be helpful.
Adios, david