You mentioned the outdoor temps changed since you last ran the truck...
Two thing immediately popped into my head:
First is winter fuel. If you live in an area that requires additives in the blend such as ethanol etc, that can cause leaner mixtures since they effectively add more oxygen to the gasoline.
The second is ambient temperature. To a point, an engine idle RPM will increase as the mixture is leaned...up to around 16:1 air fuel ratio where it will begin to drop. Cold weather and a cold engine require a richer mixture to maintain a given RPM compared to say a 80 degree summer day.
Not knowing when and where the engine was driven prior to your project, I would assume it's been awhile since it was last jetted for the locale.
Discarding everything I mentioned in my previous post...
I would do the following:
Check that the fast idle cam is dropping out after the choke is opened fully. The choke plate can be open but the fast idle can CAN stay engaged sometimes. It's the red plastic item in the top center of the photo.
It that's not sticking then I would completely close the carb's throttle plates by backing out the idle speed screw.
I would close both idle mixture screws, then back them out 2 turns.
Next I would open the throttle plates with the idle speed screw until the engine would idle on it's own at about 650-700 RPM in neutral.
The proper setting should just uncover the bottom edge of the idle speed transfer slot. (Can't see this unless the carb is off the engine)
Once the engine was fully warmed up I would adjust the mixture screws 1/8th of a turn at a time until I found the highest manifold vacuum reading and/or smoothest idle. If no vacuum gauge is available, adjust mixture for highest RPM.
I would then adjust the idle speed screw to achieve the idle RPM desired.
You can find a quickie adjustment guide here: http://documents.holley.com/199r10268-4rev2.pdf
I'd let the engine cool down completely and run it to see if the idle changes after warmup.
Keep in mind that in a properly adjusted Holley, the main jets size is pretty much irrelevant as long as they are big enough to allow fuel to flow through them and into the idle and transfer circuits. If you can get the curb idle speed set and idle mixture adjusted the only other thing you may need to do is change main jets so your mixture is appropriate for your altitude.
Sorry for the dissertation sized posts.
