I'm starting to dig into the control panel for the fresh air / heater. The following pictures show you how far I can move the three levers. Any ideas how I can get the full range of motion? Do I need to lubricate the cables or disconnect them? Any assistance would be awesome.
Click to view attachment
Click to view attachment

Still looking for tips on this

Look at the other end of the cables where they connect to the air distribution box in the frunk. They might need adjustment or lubrication

I notice the two that won't move through the whole range are the ones that move the flaps in the air boxes and determine how much goes up vs how much goes down. If your car is early (pre-'72) someone might've left pens or pencils on top of the dash and they rolled into the defrost outlets at the base of the windshield, fell into the air boxes, and are now blocking the flaps from moving all the way closed one way or the other. I know it sounds silly, but this happened on my car and I broke one of the air box flaps trying to force the lever. I found out what had happened much later when I had occasion to take out the air boxes. You can check for this simply by removing the grilles on the outlets under the dash. If there's anything there it will fall out when you do this. The later cars have some ridges on the inside of the defrost air ducts, which I believe are there to prevent this very thing from happening.

How important is function to you ?
It is not an easy operation.
The only thorough way to know where the resistance is is to remove control panel
and the cables.
By doing so you can verify that the side valves and the center flap are free.
With the control panel out the cables can be evaluated and cleaned and the wire
straightened. Or replaced.
Identify and label each one so they are returned to proper location.
The holding clips leave marks that help in returning each to original
adjustment.
To get all three levers to move over their full range without any 'spring back'
will be an achievement.
While you're at it check for damage at the sliding electrical contacts for the three
speed fan. They are often melted. If very bad the only remedy is replacement.
Lever effort can be adjusted at the center pivot.
Your chrome face trim will clean up and look new.
The black facia can look great too.....how patient are you ?

Thanks for all the advice. When I have a few days off and a lot of patience I'm going to tackle this one. You guys are the best!