mallory distributor

Well I cant really give you any pointers about your setup but that car looks hot! Wheels look great on that!

A 450 cfm Holley 4bbl is a waste of time and effort. Most 2bbl carbs on Ford V-8 engines were 500 cfm.
Nothing wrong with a larger carb. It just needs to be jetted correctly for the needs of the engine. If done so correctly, it will work just fine.
Example: If a engine uses 600 cfm of air, and a 750 cfm carb is installed and jetted correctly, it will run just fine, the extra 150 cfm of available capacity of the carb will never be used.
Think about it. When a 500 cfm carb is on a engine, and the engine is only using 200 cfm of air (part throttle), does the car run rich? No, it is jetted to provide the right amount of fuel for the air entering the engine.
Same holds true for a carb that can provide more fuel/air than the engine can use at WOT.

The stock 1966 289 2V Autolite has 1.14 venturis and was rated at 300 CFM. You don't want to go too large on a stock to mild 289 or your drivability and fuel milage will suck. Believe me, I know (been there done that). You'd probably be happier with something like a 500 CFM Edelbrock. Remember, the stock 289 Autolite 4V from Ford was only 480 CFM and that extremely mild camshaft in your engine will not crank out high RPMs.
The distributor will run well, but it does not have vacuum advance, so that will hurt your mileage.