383 Wont Idle with new to me 800cfm DP. Idles and runs ok with Edelbrock/AFB

Mattax said

I slower turn the idle screw back until it gets to the idle circuit and it dies.
It was on the 'idle circuit' the whole time. (At 1800 rpm really unlikely the boosters started up. But you can look. ) The 'idle circuit' supplies fuel above idle. The idle ports are only a branch of that circuit.
I have adjusted the idle mixture screws out up to 4 turns and no change
Not surprising they lose effect above 2.5 turns out or so. What happened when you ran the screws in?
If you want to give it another try, set the transfer slot as mentioned above. WRITE DOWN how many turns of the idle stop screw it takes to reveal .020. .030 and .040 of the transfer slot.
When on the engine, it should be no more than .040 once its warmed up.
What's the initial timing at? 800 rpm? 1000 rpm? 1200 rpm, 1800 rpm? Within reason you can pickup some rpm by increasing the timing. Going to guess it will want at least 16* and will probably like 18* initial better, maybe as much as 20.
Is this a case where drilling holes in the throttle plates is in order?
Yes. But it seems too far off and too little info to jump to concluding that's what is needed.

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Maybe I need to try and describe the Symptom a little better or at least with more detail. When I initially installed the carburetor, it would not idle at all. I could keep it running by holding the throttle open. Using the idle speed screw I turned it in until I was able to release the throttle without it stalling. This was at a about 1800 rpm. I then screwed the idle mixture screws all the way in and then backed them both out 2 turns. I then tried lowering the idle speed and adjusting the mixture screws in and out. Giving it a bit of throttle input when ever it would start to die. The mixture screws had little to no effect regardless of position. At one point I think I had it idle down to 1200 rpm but one goose of the throttle and it would not idle again.
As far as initial timing, I will have to recheck that. I set it at 33 degree total timing at 2000 rpm. I did not suspect a timing issue as it runs normal with the old carburetor. For the record the distributor is an old Mallory Dual point with no vacuum advance.