Trying to decide if I should switch the Campione drops to my longer 3TTT stem that has the Giro bars ?
Im switching the stem and the Giro bars are in slightly better shape and look more chrome like than the duller alum Campione bars. Is it worth the effort to get longer and wider reach ?
The Campione also have a cable indent built into the bars to help keep the taped cable in place.

I believe the specs are:

The Giro (Cinelli 64/40) has a 138mm drop and Campione (Cinelli 66/44) has a 158mm drop. The second number in the stamping on the top part of the bar is the width in centimenter measured center-to-center at the cut ends, as in 64-40, 66-42, and so on.

Anything else Im missing in this decision ?

26.0 vs 26.4

The Cinelli CdM's are popular with many C&Vers because of the very elegant, big, circular curves they have, transitioning from the top to the drops, but I doubt if everyone can handle such a deep drop on a handlebar. I myself find them a bit too deep, despite my being very used to riding on the drops for long periods.
So be sure you really want to go that deep with your drops before you change out to CdM's.

That is why Cino made the CdM #63!
If you are big, go wide, and consider a shorter stem, the #66 throw more forward.

I'm a 64-42 guy and like the horizontal drop ends with real estate. Not the greatest for STI's, but will work just fine. Some say they were not made in 64-42 but I've only ridden about 6 sets in that size.

The "sleeve" will also shine up fairly well once you get the anodizing off.

Just updating my decision to go with the CdM Campione (Cinelli 66/44) with the longer stem and its an even better fit as I hoped for. I do notice the deeper drop and finding my comfort level quickly getting use to this lower and more aero position. Will take awhile to stay low for longer periods as I like to spend more time with my hands rested along the top curves.

Not sure what this diff is but I am happy to report I no longer have any creak when pulling the bar ends.
The 3TTT stem is odd in that the nut is recessed in the stem such that a standard allen wrench just reaches it for setting the stem tight into the head tube.

My preference is the Campione d Mundo, but in a narrow width. With 44mm ctc the drop can be an issue, but pull the bars tighter and the effect is minimized. Flatter ramp out to the hoods is easier on CdM version. That said I have more Giros on bikes.

I do not remember ever seeing 3TTT wedges bolts recessed as deep as you describe but they have recessed them a bit to allow for using a cosmetic plastic cover that is pressed on to the socket of the allen head bolt to present a smoother, more aero look to the stem. Unfortunately, many owners of these aero stems lose or mangle up the plastic caps when installing and adjusting these stem through the years. Worse yet, these plastic parts on late 80's aero stems tended to degrade, crack and fall off on their owners....