1972 Demon 340 engine mods

This car had this carb for a few years, the way it ran deteriorated over time.
I put 64 jets in place of 72 jets without change. I also put new power valve, reset fuel level, put all set of new seals on the carb, cleaned it and still no change. It shakes all over the place. Heck I even put old 600cfm Holley fully rebuilt and it acted all the same.
This is why I’m looking for source of problems elsewhere.