Most believe 2 x 4's will loss a little horse power over a single four. However, when tuned correctly many have seen increases on a dino over a single four. Though you may need to increase the cam a little in your motor for them.

I ran 2 x 4's on a '62 vette back in the sixties and loved em, never had to fuss with them much more than a kid would anyway. I run 2 x 4's on my current ride and love em. Gained a slight horse power increase once they were dialed in and motor sounds throatier (deeper), especially when floored (lol). Have not had to fuss with them any more than I have with a single carb. Although I do get a little less mileage depending on my foot.

IMHO, the key to success with 2 x4's is getting them sized and tuned correctly in the beginning. I'm currently using the Edelbrock 2 x 4 set up. While it was a little pricy, it comes with matched carbs that are tuned pretty close out of the box, both carbs have adjustable vacuum secondaries which help tuning the motor CFM requirements. Didn't take much to dial them in, and their instruction are very comprehensive covering everything you need to know (and then some).