Awesome Gregory :-)
Now for the "more complicated" part...
I've measured the selector in my '88 Spoiler and the pan pot in my Orion, the pan pot is about 3,5 mm taller.
There is some clearance between the top of the selector and the closest component on my '88 board, but it will be a tight fit...
+ I doubt the pinouts will be the same, so I think you'll have to use wires to connect the pan pot to the board.
There is very little room to move the board out of the way needed, make sure nothing is touching the Silver shielding paint (!)
If it won't fit, I think the best option would be to replace the complete package with an Activator set. (easiest, but way more expensive option)
Most intrusive option -if the pan pot won't fit- would be to route out the cavity under the battery (so you can have the main board angled, a bit like my '83)