carb size

hey guys need help on 2 things .. 73 mustang conv    351c 2v ..redid heads and have cam not 100% on size and duration. 2v to 4v intake added headers and my carb is a 750 double pump ..question is would it be better to go to a 600 or 650 ? runs good just wondering if smaller carb would be better and if so why ? .. other question is I need tires what is a good setup ? installing new leaf springs and shocks next week and thinking 255/60r15 for rear and 215/65r15 for front

Depending on the cam, 750 may be a little too large for 2V heads. It should let you know when you floor it, does it bog down at low speeds, or stumble or bog down when you're driving down the road and floor it? I wouldn't go any lower than a 650, if you decide to change. A smaller carburetor will typically give you better throttle response and better mileage.

Your tire combination should give you a nice staggered look. Make sure the rim width matches your tire width and wheel offset is correct for your wheel width. Tire sizes have been discussed many times on the forum, if you type in "tires" or "tire sizes" or "wheels", or any combination of them under the Search icon at the top of the page you'll get quite a few threads about it. There are a lot of pictures of what members have put on their cars.

Please go to the Introduction section under Forums and introduce yourself and your car. Be forewarned, we like pictures.

750DP will be okay on a 2V. You need to tune your foot to what the engine can take at what RPM. Would a smaller carb be "better"? Maybe, depends on the engine and as you said, you don't know the cam or what's been done to it. How does it run now? If it runs fine, are you happy with it? If the answer to both is yes, would I spend a bunch of $$ to replace it? No.

A modern equivalent for the original F60-15 is a 235 or 245/60R15. They'll fit with zero issues on a stock offset rim. I've run a 275/60 rear and a 255/60 front, with only a minor rub on the frame by the steering box/idler arm at full lock.

Standard or auto? A "double pumper" is a mechanical secondary carb and will work best with a standard while the autos really do better with a vacuum secondary carb. You can better get by with being over carbed with the vacuum secondary carb as it will somewhat self regulate where as the mechanical secondary is purely at the mercy of your foot.

it is auto and it runs good I just have been told my 750 is better for top end rpm and 650 is what I need.. I will try to get pics this week since im not sure what my carb is

The "double pumper" moniker is just as synonymous with "Holley" as "Cleveland" is with 351 Ford. Nowhere near all 351's are Clevelands just as nowhere near all Holley four barrels are double pumpers.