If you are planning to use the engine for mostly street driving, not for racing, there is little practical sense in going to a 4v carburetor, IMHO. Those Autolite 2100/2150 carbs are really decent. They are durable, easy to adjust, easy to rebuilt (when/if ever required), and not all that finicky - really just an all around good carb. The only real weak spots are over their their throttle shafts can get worn in dusty areas, and their Power Valves tend to leak over time. If you plan to do street driving, no racing around, You are just as well off leaving the 2v in place. The 4v carbs will not increase power that much unless you open the engine up with other options to help it breath better - headers, high rise manifold, higher combustion chamber compression ratio, more aggressing cam and valves, lighter internal components (pistons and rods), etc. You may "feel" the engine is more powerful just slapping on a 4v carb, but the reality is you mostly just "hear" more of the engine roaring through the intake, unless you are using the pure stock air filter housing which will dampen that extra roar quite a bit. So, it may "sound" like it is putting out more power, but if measured in a 1/4 mile strip run you will gain little, if any significantly measurable difference.
Part of that is because engine likely will not be built to take advantage of the larger CFM of a 4v carb (in fact if you go too large it will be a detriment at some point). Part of it is because a lot of those Mustangs with 302 2v engine were built with fairly steep rear axle gearing (2.79:1 - 3.0:1 ratio), which is good for fuel economy and low RPMs at highway speeds. But, they are terrible for off-the-line performance. So, even if you built a higher HP 302, much of that power will be buffered by the rear axle ratio for cars with higher ratio gears. You would need to move to a 3.5:1 rear axle gear set to begin to get lively performance, or to be able to truly feel the difference of a higher horsepower engine. But, with 3,.5:1 rear axle gears you will be turning about 1,000 more RPM at 60 MPH as compared to 2.79:1 gears. Everything about building a car for higher performance is a trade-off, including with money. The more power the more cash is being burned. And the cash burning continues for as long as the higher performance features are in place. Lower MPG with the lower rear axle gear ratio will be in place for as long as the lower gear ration is being used, for instance.
Anyway, if you have a 302 2v in a stock pony car, one of the next things you can do to improve performance and make you feel like you are in a sporty car, is to move to a dual exhaust system. And, have an H or X Pipe installed. From what I have experienced, and seen (Engine Masters has a great segment on this), both an H or X Pipe will alter the sound of the dual exhaust, but neither adds all that much more power to the engine - you likely would never feel it, nor be able to measure a significant difference in performance. But, the X-Pipe is allegedly less raspy sounding with a moderate street strip level engine. I installed an X-Pipe on our non-stock 1973 Mach 1 (351W [not C] with a 750 cfm Holley, vacuum secondaries), and long tube Hooker ceramic coated headers, beefy 3/4 race cam, high performance forged aluminum pistons, (plus other internal and external performance items). The first things folks tend to say is 750 CFM is too large for a 351, and I would normally tend to agree - to a point. But, this 351 is built up in other areas that make the 750 cfm a good choice. Plus, it is a vacuum secondary carb, which is more tolerant to being over-carbed for street driving. Anyway, the X-Pipe certainly did take the harshness and drone from the exhaust, and the engine's normal running temp dropped 2-3 degrees due to the reduced back pressure of the hot exhaust gas. For me, had it only smoothed out the exhaust gas sound I would have been happy enough.
X-Pipe vs H-Pipe: