Now that you got the timing where it's decent, focus on the carbs. Like Dayclona says.....could be end carb adjustment OR center carb mixture is way off.
Progress is good.....just sometimes brutally slow!!!
I can't even begin to tell you how much frigging around I had to do to get my 6 pak to idle when I changed to a XE295HL Comp cam years ago. Even had to go as far as drilling 1/8" holes in the throttle plates. That would be my last resort in your case though.

I'd love to have your car for about 1/2 hr !!

I'm not sure of what all mods where done by C&J Engr. in Whittier, CA, to my vacume OEM sixpak carbs. but they would idle at 850 RPM in gear with a 260@.050 solid roller cam in my pump gas 512 C.I. low deck stroker motor. I did have to shorten up the advance so it idled at 14 to 16 BTDC at 850 RPM and it had 34 BTDC degrees total, I put a 2.5 Holley power valve in the center carb and it would idle with the outboard idle mixture screws out between 1/4 and 1/3 turn out from being bottom all the way in. The center carb had 1.0 to 1 1/4 turn out from bottom, all three carbs. ahd the 1/8 holes added to the throttle plates. My wide ban showed the AFR to 14.2+ at idle warmed up Nice clean throttle response, no bog at all, ever Not so for the stock 1971 OEM replacement carbs. I bought from Mopar They needed a lot of massaging to get them to run with in 1/10 of the modded. carbs. BTW, that motor hopped up with aluminum heads and more compression(10.29 to 1 ratio)had a best 60 ft. with a 1.39 on pump gas through the muffs on motor only foot braking

have you checked the volts on the coil side of the ballast? I chased an issue like that all weekend once, wouldn't run at all below 1300 or so. Ballast was bad, not enough juice to the coil.

Ok I'm back and still chasing this problem. I have since replaced the intake and put a new center carb on. And have now discovered that I'm not getting fuel to the carbs.
I disconnected the fuel filter (between the tank and pump) and thought that I'd check to see if I got fuel coming out the line from the gas tank. I did my best to blow into the tank and I was able to get fuel to flow out not a lot but some.
Next, I disconnected the pump and cranked the engine with no fuel coming out. I took the pump off of my other big block (383) and replaced it. I will mention that the pump I took off of the 440 did not appear to be working and had a hole at the top. After replacing that I still can not get fuel to the carbs.
The only thing that I couldn't do was run a line from the pump the to the carbs bypassing the FUEL VAPOR SEPERATOR (I just didn't have an extra fuel line).
Anyone want to put in there ?
Gas / Fuel Tank Sending Unit plugged? or Fuel separator plugged?

first I don't think you should have a filter before the pump. second, is the pump rod in good shape? can you manually move the lever on the pump and get fuel to come out?

I agree, I was surprised to see the filter between the tank and pump. The fuel pump has a hole about 3/4" x 1/2" on top, and I know it shouldn't be there. Lever on the pump does not move up and down like the one I put just put on.

All of the lines check out. The 383 pump that I had put on is not pumping. I pulled it and started to put the original on and saw this.

What if any is the easiest way to install the pump? Laying on your back and trying to line up the holes with the filter is a [Edited by Moparts - Family Friendly Site - Keep it clean].

Take off the alternator...at least then you can see what's going on. Like mentioned....make sure the push rod for the pump is staying up inside the block (turn the engine over until the rod is up in the block all the way). Use grease as shown to hold it there until you get the pump positioned.

Finished installing the new fuel filter (because of the hole) rechecked all of the plug wire (a couple were burnt by the headers).
My Mopar Buddy (came from 4 hours away) did the following:
1-disconnected the accelerator & kickdown linkage, then reset them
2-adjusted all of the fuel mixtures screws
3-adjusted the curb screw (it was way really off)
4-checked timing reset to 38 @ 2400
5-re-set the float level on all carbs (the new one was way off)
In less then 45 minutes Dave got it dialed in. Finally it idles and I can put it in drive without the engine stalling.
Thanks to everyone for the help.
To some it up I had a cracked intake at the 7 port.
I'll check back if I have any other issues