detonation / knock issue on 340

also noticed that the carb to manifold gasket is very thin, this is my first go around with a holley, ive always been a thermoquad guy. the carb to manifold gaskets were always thicker. i am asuming with the leak either the base of the carb or the manifold plane is not 100% flat. would a thicker gasket help solve that?
Start here you need to make sure the engine is not sucking extra air.
Spray around intake and carb. Find leak.
Then you can start checking carb(which is way to small imho), timing and ignition.
Also what are specs of engine?
Cam
Pistons
Compression ratio
Heads