Its OK for stock and can be part of the strategy for modified as long as you understand the limitations.
a. The timing has to be established.
The reason for this is that continuing to advance the timing will continue to increase the manifold vacuum and also allow leaner mixture In Neutral. When put in gear, engine rpm (and vacuum) will drop bunch. This is because it is too lean to make power at idle.

b. The relation of the throttle blade to transfer slot has to be within working range. Old school Holley was .020 to .040 visible. Newer carbs sometimes have longer or wider slots but somewhere around square is a starting point.
Tip. When the carb is off; note the number of turns of the idle speed screw from just touching to .020, 030 and .040" inches. Write this in your notebook.

IF the transfer slot relationship is correct, then gentle acceleration from idle to off-idle will gently accelerate the car. If it gets blubbery or it hesitates and then goes, then some adjustment is needed in the idle circuit only after some trials to be sure the transfer slot relationship and timing can't be used to fix the situation.

And to compound the issue it's an auto with a fairly tight converter so the rpm difference between park and gear has to be close

Doesn't the cam have a lot to do with the idle steadiness and sounds

you dont have to shoot for 15-1,try 14-1 & drive it,see how it does.

The thing is the plugs look fairly clean, so I don't fully believe the AFR at idle has been 11:1 for the past 3 years.
Tune for driveabilty, efficiency and power. To rephrase another persons post, use the AFR numbers as a tool rather than target. As the car is an automagic, the vac reading in gear can also be used as another tool.

Typical 4stroke piston engines will idle (hot) most efficiently from 13 to 14, but can be a little higher or lower. An engine with a hot cam has overlap at idle that reduces combustion temperatures and also generally has lots of exhaust dilution. Because of these factors they tend to need more fuel to air than a combustion event with higher compression and less exhaust.

These AFRs are from the graphs in AFR Ratio Studies. See the fig 12 from Larew and 5-8 from Taylor along with Tuner's comments on hot rodded engines.

This thread may also be of interest:
Combustion Products post

Yeah I'll find a happy spot just posting for other opinions. I went around and around with the carb and timing for a long time last year and now decided to improve it because of the gas Mileage .

He said when was the last time you calibrated the 02 not the C02. Ron

Heh. I didn't read that carefully either.
a. Thought was looking for a CO2 meter ...
b. A Proform carb means that its likely the transfer slot is long or wide, the idle feed restricion is above fuel level and there's an extra 'emulsion hole'. (There have been enough of Proforms measured and posted on RFS forum to expect this is so).
Therefore establishing the correct transfer slot relationship may be more difficult. To go further in improving the carb performance, especially the "idle circuit", will require measuring and fixing these things. Once the restrictions and bleeds get outside of a certain range the fluid dynamics become erratic and less consistant. The "idle circuit" has a big influence on fuel milage especially below 55- 65 mph....