Disappointing dyno results

I have run both a 340 and 440 AVS on my 340 with good results. Both have to be jetted properly for the engine combination and altitude you are at. I am at 5800 feet so need to lean out the A/F mixture. But the engine ran better on the 440 AVS. My next carb will be the 800 CFM TQ. The 340 likes air flow.
I would run a cranking compression test and leakdown test on the engine to be sure you have good cylinder sealing and have the cam installed correctly. Sea level CCC should be in the 180 PSIG range and not much lower. And it should be within 5-10 PSI between all cylinders on a really good build. Leakdown should be less than 10% and 5% is better. This will tell you more about sealing than CCC. CCC is impacted by cam timing as well as duration and other factors such as craking speed.
I ran my 340 with a 318 cam and original AVS carb during the first Fuel Economy crisis. It ran 14.50 @ 98 at OCIR with 2.94 gears, so it was making good power even with that tiny cam. But it also got 22 to 24 MPG which at that time was highly important. I did run a desert cooler radiator and electric fan to cut paracitic load and jetted the carb on the lean side but still rich enough to maintain good power and avoid detonation. Timing was maxed at 34° distributor and 51° with vacuum advance.
All components must work on concert to optimize engine performance.