If you want more performance, go w/a single 4-barrel. If you have a Holley carb on it now, get the number off the airhorn and see what size it is unless you are sure you know what it is already. If its an Edelbrock, the number is stamped on the base. Other carbs just ask.I've got a 454/450HP Chevy Engine in my 66 Chevelle SS (it's a street car)
Currently it has a single 4 barrel
I'm looking to add more power, what would you recommend:
A. bigger 4 barrel
B. 3 Deuces
C. Dual Quads
It can matter what gears are in it, stick or auto, how you use it, etc. but a popular carb for a mild BBC on the street is the Holley 3310 750 vacuum secondary if you're using a dual plane intake.
You might need to recurve the distributor as well. Chances are you will get more from that than a carb swap unless you're running a way too small (or too large) carb.
Any real power gains will come from compression and camshaft along w/headers and possibly a different intake, depending on what you now have.