For what it is worth - what I have learned the hard way regarding Holleys is as follows...
With a carb that big (for engine size) you have lots of juice with those jet sizes - I would guess 68's and 72's would probably be much better in a final sense... but that said, and as John mentioned, a 1-1 1/2 open point for the needles is about right for primary adjustment and initial starting point.
Once you get it warmed up and get the float levels correct (very important esp. the float levels as mentioned previously) it should respond to needle changes if all else is well internally in the carb - and it should start to die out pretty much anywhere under 3/4 -1/2 turn in on the needles (again if all else up to snuff).
If it continues to idle the same as you turn the needles in or out then you probably have a power valve problem in either it is way off size-wise, or is blown out and that is why the response isn't there... Too far out of range or blown will usually be accompanied with enough fumes at idle in an enclosed area to make your eyes water to confirm this!
All of this is prefaced on the assumption that the cam you are using is pretty big and also similar to a 30-30 type but not something radically different which then throws a lot of any advice out the window as different cams create much different vacuum signals and therefore mixture, jetting, and power valve requirements.
If you have the butterflies open too much to keep the idle up to prevent it from stalling out, often the transition slots will often get uncovered too much as mentioned also and it will make any needle valve adjustments futile. This quite often occurs again when the carb is too big for the displacement, vacuum signal, or compression ratio, and the only real crutch for this is to adjust the secondary butterflies stops a bit open to get more air, to allow closure of the primary butterflies sufficiently to cover the transition slot which will help make the idle mixture screws somewhat more responsive again and get that part of the adjustment equation working hopefully... - failing that drilling a small (1/16" or so) hole in the front side of the primary butterflies can be of help to aid in getting more air in at a somewhat decent idle speed but this type of thing should only be used as a last resort and when all else fails...
Good luck - Randy