340 carb size?

Hello all. I tried searching for this topic, but I'm not having much luck on my phone. I was hoping some of you may have some input. I have a 69 Barracuda with the stock 1969 340 in it. I don't know anything about the engine really, when I got the car the previous owner didn't seem to know much either. He asked to keep his 750 carb that was on it, and gave me another 750 that it "didn't run as well with" when I bought the car. He let me take the car home with his carb, I put the other 750 on and the rear float is sticking, and keeps over flowing with fuel. This carb it came with is old and I want to replace it. 750 seems like a lot for a mild 340 in my opinion, but then again everything I own is new and fuel injected and tuning those cars is a little easier. I want to buy something somewhat ready to run out of the box. The engine has stock heads from what I can tell, sounds like a healthy cam, an Edelbrock dual plane intake, 1-5/8 headers, flowmasters, manual valve body 727, 4.10 gear. I was thinking of a Holley Street avenger series carb, people seem to have good luck with those out of the box. The question of it is should I go 670 or 770? I don't think I'll ever do more to this car, maybe a set of Edelbrock aluminum heads someday. What do ya think? Thanks for any help.