Morgan, turn both idle mixture screws in until they
"LIGHTLY" bottom out. Does that cause the idle to change or stumble (does it kill the motor)? If it does, then turn each idle mixture screw out 1 1/2 turns and see if it changes from there by adjusting in or out each idle mixture screw. The key here is to keep both idle mixture screws balanced. In other words, what you do to one mixture screw you do to the other (but you probably already knew that
).
Now for my two cents...You say in your first post that the vacuum is 2.5. You changed to a 2.5 power valve. I would say, if it still shows no results or change in idle after you give the idle screws another try (see first paragraph) then your power valve is affecting the idle. This shouldn't happen at all. The intent of the power valve is to add more fuel once it goes below that prescribed point when you open the throttle. The way it is setup now, your power valve will be dumping fuel in at an idle. 2.5 vacuum at idle = 2.5 power valve.
No disrespect to Chryco, but when he said, "Go to a 1" power valve" I went looking and came up with zip. In other words, if a 1" exist I sure can't find it? The man is a super wealth of knowledge when it comes to Mopars. However, I would say you do have one more option left. It isn't great when it comes to street, but think of using a power valve block (I would check with Promax first before doing this). What makes it unsuitable for the street is first having to run your main jets richer (I know- I know, you just changed them). Essentially, with a power valve block, you'll have two choices at the throttle. Idle and go like hell for this combo to work, but it should give you a clue IF you current 2.5 power valve is affecting the idle.
BTW - 2.5 at idle? That must be "One Cammed Bad Boy" you have there? I'm happy my 440 pulls 7! Whew!
One more BTW - Double check the metering block gasket to main body of the carburetor. I can't swear to it, but it might be upside down? Looking at the lower hole, just right of the power valve, in your photos. Needs to align with hole in metering block. Like I said...I can't swear to it...
