Watch a video about how to replace the main well tube
Spark Plugs Burn Black
This is an indication that the engine is running too rich. There are multiple reasons for this. Electrical is probably the main culprit so start there. Plugs, wires, distributor, etc.
Other possibilities are float level, fuel pump pressure too high, jets too big.
As far as the jets go you need to think this through. Jets don’t simply change size over time. If the engine was running OK at one point then the problem is most likely somewhere else. Reasons to change the jets are moving to higher elevation. 5000 ft + may require the jets to be reduced by .002. Another reason may be that the carburetor is a transplant and was jetted for a different engine.
Car Seems to Run Out of Gas
Might be a weak fuel pump. Test pressure for 4 lbs and also check volume. I don’t know what it should be. I don’t have a motors manual for 1955.
Needle may be sticking in the seat. Could have been damaged from adjusting the float, or a new needle might be covered with residue. Cleaning with mineral spirits will clean the needle.
The float may be out of adjustment. Be sure the float drops enough to pull the needle out of the seat.
Of course check the float level. Refer to the carburetor kit instructions for the proper measurement.
At Idle Engine Seems to Load Up
There is a good chance the main discharge is leaking. Look down the carburetor at idle and see if gas is dripping from the main discharge. If so, then the check ball may not be seating (tap lightly to form a seat), or the spring above the ball is missing.