New to me 73 duster 340

It’s not going to perform like a modern turbo charged engine. You should still feel the engine pulling harder and revving faster as the RPMs build with a high-performance cam. Does the car have fresh super unleaded fuel in it, or is the fuel old? Also, with the engine off and the air cleaner off, if you actuate the throttle lever on the carburetor, do you see it squirting gas into the primary side of the carburetor? The accelerator pump definitely needs to be working on the carburetor to get it moving. A carburetor that needs to be rebuilt definitely won’t do any favors for the way the engine runs.
I don't drive my 340 Dart much these days, about an hour each month, to keep things in working order. I do need to replace the accelerator pump every two years.