I bought a Nostalgia Kegerator for $40.00 of CL but it didn't have the tower with it. I bought a 3" single tower(should have bought a three tap!) and had to drill all new holes. I went all the way through the top and almost screwed up big time. The front two holes went fine but when I drilled the first back hole it felt like it went all the way through then stopped. I drilled for a second or so longer then decided to check. Good thing I did, I was about to drill through the coil that was mounted on the back. The top of the coil wrapped under the top a an inch or so and I didn't think
that it came out that far. I had to un-mount the coil, use a thinner mounting plate, and go with shorter screws.
Sounds like you had an easier time. That looks like a nice setup.