Cleveland heads
I can only assume you're talking about Cleveland heads here.
All domestic 351C-2Vs had open chamber heads. All 2V engines had flat top pistons. If you put closed chamber 4V heads on your engine, you'll end up with around 10.5 to 11:1 compression. Do you really want to go that high on a street engine? You'll have to run 93 octane or higher gas all of the time if you do. How is the rest of the engine? Will it take the added stress?
Also, if you go with the 4V heads, you should also get the matching 4V intake and exhaust manifolds since the 4Vs have much larger intake and exhaust ports, otherwise, you're really wasting your time. Well, they'll make more power than your current 2V heads, but 4V Clevelands really like to breathe!
You can get aftermarket 4-bbl intakes for your 2V heads if you really want a 4-bbl. They will still have 2V port sizes, which are really all you need, but you can bolt a small 4-bbl carb on it. I'd go no higher than a 650cfm vac sec carb on it. My 'Beta Cat' is a true 4V and I'm running a 600cfm vac sec on it and it does quite nicely, lots of torque, and still rips off 14.40 passes all day, every day throu the stock dual exhausts.