Unsteady idle

[Malibu72]

Hi,
      Got a 72 Malibu with 30 over 454, 10 to 1, Crane 226/236 534/553 cam, 14"vacuum. It will not idle decently in gear below 850 (th400), and even above 850 its not that great. Vacuum gauge is fairly steady which is what has me puzzled. Even disconnected and plugged the vacuum line to the distributor to eliminate the advance jumping around. I thought that it should be able to idle around 750 in drive - maybe I'm wrong. Otherwise, car runs great. 
The carb:
       17082227 - 800cfm from 82 305 Chevy van.
        37 idle tubes, 52 down ch restrictions
        67 upper idle bleed, 70 lower, 093 idle needle holes
        .085 main air bleed (single main air bleed carb)
        77 main jets, 52m primary rods.
        Cliff's kit and Cliff re-bushed my base plate.

Also, sprayed carb cleaner around looking for vacuum leaks but found none.
Appreciate any ideas on where to go next. Thanks.

[Cliff Ruggles]

How much idle bypass air?

I'd open up the idle down channel restrictions to .055" and see if it helps?  If it's better, but not ideal, go up to .059".....Cliff

[Malibu72]

Opened up the DCR from 52 to 55. Idles good now at 725rpm in drive. No more exhaust smell and got rid of a very slight off idle dead spot. Also start up when cold is now fuel injection like! Engine barely cranks and it running. BTW, idle bypass is .110. Thanks Cliff!

[Cliff Ruggles]

Good news!......Cliff