New Carb problems

I joined this forum to get some advice on a new carburetor I got last year. I own a '69 cuda fastback, with a 340 small block automatic. After almost 40 years, the old carburetor was sputtering and choking and needing either a complete rebuild or a replacement. I went with the replacement as I'm in a small Canadian town and muscle car specialists are hard to find, and I could get my old one rebuilt at my leisure. I went with an Edelbrock Performer series 1406, a relatively straight swap. Now, I fully admit I'm not good with carbs and the tuning thereof so I figured I'd throw this out there to anyone with better knowledge and a possible solution.

The car immediately started running better with the new carb, but when I start off the line from a dead stop, there's resistance on the gas pedal, as if something's preventing it from pressing down all the way. As the car gets moving, I can feather it (lift back and press down again) and get the pedal down a little more until I'm at a sufficient speed. There's nothing wrong when I'm actually moving, but at stop and slower speeds, there's resistance and strong enough to prevent me to put it down to the floor. I'm a little disconcerted with this particular problem as A) it's not fun (can't lay a patch) and B) it's dangerous when I'm trying to quickly pull into traffic. I'm just wondering if the carb was incorrectly installed/tuned, it's a built-in safety feature or my engine just isn't strong enough to turn the tires anymore. Hell, maybe I'm running the wrong carb.

I'm running P245/60R14/98S in the back, a good 9.5" of rubber connecting with the road and P235/60R14/96S in the front. I'm aware they're wide, but my old tires weren't that much smaller and I could still burn them with the old carb. Any help would be appreciated. Thanks!