IF those plugs on the carb are leaking, that means the ethanol-content fuel has eaten away the sealing solder from around them. They'll need some new "sealer" around them to stop those leaks/seeps.
When I upgraded from the WWC3 carb on my '66 Newport to a '70-spec Holley 2210 carb, I used the supplied "thin" base gasket. All worked well, but after a week or so, the idle got a little more quiver in it. I got the wrench and re-torqued the hold-down nuts on the base of the carb. Fine again. Cycle repeat. I got an OEM "thick" base gasket, as the WWC3 had had, installed it, gently torqued it to "snug", rechecked it a week later and it was still where I tightened them to. No further issues with idle "roughness".
Not sure where a lean surge might be coming from unless there's a vacuum leak somewhere. Choke pull-off?
IF it runs excessively rich while the automatic choke is closed, THEN it's probably got the "air cleaner wingnut over-torque syndrome! That means the integrity of the seal between the air horn and the carb body has been compromised as tightening down the air cleaner wing nut, over time, will deform the center of the air horn (where the air cleaner stud is anchored) UPWARD. When that happens, the vacuum which would keep the power valve normally closed is lost, so the power valve is always "on" and mpg drops to about 10mpg or so. When the automatic choke valve is near-closed, raw fuel can be sucked over the top of the float bowl, between the carb body and the air horn, and into the carb's air flow into the engine. Over-rich and stalling if you don't manually throttle into the carb to keep the engine running. Been there, done that.
CBODY67
