Kegerator: Danby model xxx with a 2-1/2" diameter tower.
Process:
Remove the spout wit a spout wrench
The tower top is not threaded and comes right off.
Undo the collar nut on the interior of the tower.
Remove the shank assembly and beverage hose.
I used a 7/8" hole saw. Make sure you use a nail or nail finisher to put a small dent in the tower to make sure the drill doesn't wander on you.

I had to locate my 2nd shank lower than I wanted to because it would have been overcrowded at the same level on a 2-1/2" diameter tower.
Don't forget to slide the decorative base over the tower before installing the shanks. Ask me how I know.
Thread your beverage lines through the tower and secure them to the shanks before mounting. I cut the tabs off with a Dremel to make it easier to slide the collar nut over them.
Mount the lower shank before the top one or you won't be able to reach it. Put it all back together and enjoy two beers, you earned it!