Modifing Factory Gauge Tins for Factory Tach

[D-n-Tyke]

I am looking at putting a OEM tach in my truck. My gauge cluster did not come with a tach so the tins are not set up to accept the tach. I am assuming someone has figured out how to modify the tins so a tach with fit/work. Does anyone have pictures/instruction on how to modify them?

(In my search I found a member named Coley that offered to send people instructions on how to do this. But seems like he hasn't been on the sote since 2001. Anyone have the instructions he was sending out?)