ok here we go
here you can see i've drilled a small hole in the top of the cluster case so I can adjust it with it almost completely installed in the truck, If you plan on doing it this way, I suggest you remove the board before drilling the hole or you could chip the board and have to solder it back together like I did.
Remove the lens and the gauge faces
It'll look something like this
Locate the potentiometer on the tach board and mark your spot on the case to drill the hole (the little blue box with screw.)
The screws that hold the tach in go through the back of the cluster where my three fingers are
Remove them and lift the board out