[VetteVet]

The two most common reasons for your symptoms are the accelerator pump in the carburetor is bad or out of adjustment, or the ignition timing is off.

Pull the air cleaner off while the engine is off and climb up where you can look down the carb throat, then manually work the throttle and watch for two real good streams of gas to go down into the manifold. If you see a trickle or nothing then the accelerator pump is bad, or the rod for it is out of adjustment.

Loosen the distributor hold down clamp just enough to turn the distributor and turn it clockwise just a small amount while the engine is running and the engine will speed up.
It should perform better, if the timing was too retarded. If you have a timing light you can set the timing where it should be. Probably about 10* BTDC .

If neither of these help you may have a badly worn timing chain and that will also cause acceleration problems.