On a 65/66...like mine and Sal's...you can neatly install the servo at the right end, behind the dash, right next to the glove box.  Then let the cable make a nice clean sweep up over the glove box, behind or above the radio,to the firewall.  Only thing you see under the hood is a short piece of ball chain. If your unit has a little stick-on button cluster for controls, you can buy a Rostra "slip-over" stock from Summit and attach it to the turn signal lever (gotta cut the lever).  This may require changing one or more dip switches in the servo.
I think Steve and Glen B also mounted the servo unit from a Rostra electronic cruise control in this same location on Steve's 67.  I think they mentioned that the electric servo makes a clicking noise that is annoying.  May be they use a "duty cycle" motor on those.  The old skool vacuum servo I have is dead quiet....not that my ears would notice.
Also, you will want to get a late 80's /early 90's ford VSS (vehicle speed sensor) and a speedo cable that will also connect to the VSS.  That is unless you already have an electronic or GPS speedo.  Don't mess with the magnets on the driveshaft method.
 

Although I do not have cruise control, I did have a custom speedometer cable made for my needs.

Cable has threaded connection to factory gauge and foxbody push-in do hickey at transmission.

Factory EFI uses vehicle speed sensor (VSS) for deceleration and cruise control.

60” cable works for me.

‘65 speedometer (5 gauge)
‘92 T-5 transmission
Foxbody vehicle speed sensor (VSS)

This is who made my speedometer cable:

‘ https://speedometercablesusa.com/




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I put my Rostra servo mechanism on the sloped side of the passenger floor board on the outside of the floor panel.
Of course, I did make all of the necessary splash shields and waterproofing of the unit.

The unit I  have has a really long cable and could not bear having an ugly cable coiled up under the hood.
I marked the location from inside the car and used steel riv- nuts to mount the unit.
The company, Rostra, said the actuator cable was no shortanable, is that even a word!