Kenth - I do not necessarily disagree with your post on enlarging the idle circuit; I simply do not have ALL the calibrations on the smog Rochester carburetors to make this recommendation.
I do have these calibrations on both Carter and Stromberg carburetors. The engineers knew that enthusiasts had been drilling jets since at least the 1930's, so their solution to minimize "tampering" was to install LARGER gasoline jets on the smog carburetors; but also MUCH LARGER air bleeds. Thus the key to enrichening the mixture on these units is to pull the air bleeds, and fabricate new ones of reduced size. They figured the average enthusiast did not have the necessary tooling to fabricate smaller air bleeds. A lot changed on carburetors from 1967 to 1968, and more so each succeeding year.
The fact that the OP has stated that the hesitation goes away once the engine warms suggests to me that the missing choke may be the culprit.
And, even if making the choke operational fixes the hesitation; drilling the idle circuit MAY still be of benefit. Some A/F readings would be helpful in making that determination. But I would suggest working with the choke first.
Jon.
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"Good carburetion is fuelish hot air". 
"The most expensive carburetor is the wrong one given to you by your neighbor".
If you truly believe that "one size fits all" try walking a mile in your spouse's shoes!
Owner of The Carburetor Shop, LLC (of Missouri).
Current caretaker of the remains of Stromberg Caburetor, and custodian of the existing Carter and Kingston carburetor drawings.
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