I'm your 65-66 C body Autopilot guy - PM me for questions and answers.
FWIW, the dash hole can be drilled out and finished with files - make a template from the parts car.
You're going to need a lot more than the switch from that parts car - the gas pedal pivot is unique, and you need to be aware of fitment issues with the servo if you've got upgraded dual res master cylinder. Make sure you grab all the specific brackets for mounting the servo underhood, and make a template for the holes on the inner fender.
While the bezel you show is correct, the actual dash switch I see in your picture looks like a 64 and older, and is not correct for 65/66 AFAIK - in 20 years of refurbing these systems that's the first I've seen where the two were in use together, so unless something's been macguyvered, the dash switch will likely NOT fit the bezel and work together properly. On the correct 65/66 dash control there's a specific numbered dial that shows through the window in the bezel, which I don't see in your picture. If you don't have that you'll be guessing as to the speed setting even if you're able to get the bezel and switch to work together.
As well, the dash dial for all 65-66 C body Autopilot systems is prone to age-related failure due to a plastic gear set that cracks and falls away from the metal shaft. I rebuild the dash dials (I advertise in the WPC News) and get a few done every year for people. The other caveat is the electromagnet assembly that is part of the dash dial control is EXTREMELY fragile and if it gets broken, it's game over for the switch, at least in terms of what I can do with it. Coupled with the plastic mounting clip for the electromagnet coil that is as brittle as a potato chip and snaps by simply breathing on it, you've got a dash dial that needs careful handling to survive. I've repaired more than one clip with JB weld and metal reinforcement.
There are specific holes required for the firewall (for the gas pedal pivot and the bowden cable from the dash control), the two speedo cables are unique and the lower speedo cable is 65 ONLY, so make sure you grab that, and don't mess it up coming out of the trans, very hard to find.
The actual servo is fairly easy to get working - there's internal point sets for accel, decel, and cruise that need to be dressed and set in the right position or unintended "locked on full acceleration can occur", which is why they went to vacuum controlled cruise systems by 68. They made it seem like rocket science and it became a remove and replace item when it was really a simple maintenance issue, but such is life...
As well, inside are things like fly weights and other parts that need lubrication.
Let me know how I can help.
