OK. It is difficult to setup a choke, even a manual one. Later you can see if anything can be done by adjusting the fast idle relationship to the choke position.
On an older automatic chokes there is a vacuum actuated 'pull off'. When the engine starts running, the choke opens further due to this pull off. Your new manual choke should cover that vacuum hole. I can send or post a picture if you need.


3310-2 Should be a good carb as long as it has new gaskets.


According to Holley's List, it originally came with # 72 Primary Main Jets, and a 6.5 Primary Power Valve.
Neither of these will effect low rpm.


Just to verify, the vacuum advance hose is going to the capped nipple in the photo you posted?
If so, then the only way vacuum is going to that port is that primary throttle blades are open to far at idle.
The pop in the exhaust is probably a combination of ignitable mixture (unfired fuel/air) and late ignition timing making it hot enough to fire at or after the exhaust port opens.

Based on what you've written, the initial (idle) relationship of the throttle blades to the transition port needs to be brought into correct range. The transition port below the throttle supplies fuel, above it supplies air.*

Remove the carburator and visually set the primary throttle blades so between 0.020-.040" of the transition slots show beneath the throttle. WRITE a note to yourself of how much the idle speed/throttle screw can be turned from .020 to .040"
This way, you won't have to take the carburator off again to know where it is at. Use a drill bits or spark plug wire gages to estimate the opening.

Clean the spark plugs, start the engine (opening the throttles as much as needed to keep it running). Increase the base timing from 16 to 18 or even 19 degrees and see if it will idle when the throttle is brought back down to the .020 to .040" range. You'll have to adjust the idle mixture screws several times as the engine warms up and as you bring the throttle position down. The mix screws can be anywhere from 1/4 to 2 turns out, but something around 1 to 1 1/2 is most common.

If this procedure alone does not succeed in allowing the throttle blade to be closed to the proper range, there is another factor we can address. This is the air supply.
If the engine idle speed is too low with the throttles in correct position and enough timing, more air can be let pass without opening the primary throttle blades.

Traditionally, this was done by drilling a small hole in each throttle blade. Holley did it at the factory on a few carbs.
Other places air can be let in is from the PCV valve (using a fixed orifice) or changing/modifying valves. With a vacuum secondary carb like yours, another method is to slightly open the secondary throttle blades. A little bit should not effect the secondary opening performance. Again, WRITE a note of how much you turned the screw. Otherwise you lose the factory baseline.