Mopar 440 down on power
The main thing that I see is the 516 heads, the ports are very small in comparision to the 346 heads regardless of the valve size. They are down some 20 cc's less than the 346's so this is the first power loss. Then the timing would need to be a bit higher than 2*, I would think that somewhere in the 6-10* for starters, but every engine is different so go with what the engine likes. Then I would adjust the carb screws in or out until the engine runs at it's best, smoothest. This will have to be readjusted again later as the engine breaks in. I would do this for starters then let us know what happens.