The first thing you have to do before building any mod is decide where or how you want to mount it. I found 2 different ways to build/mount IR sensor. You choose which works for you.

The first way is building everything "under the hood". This means everything is built in the serial hood or small project box in the back of the computer. Although you probably won't be able to fit everything in the small hood, you will be able to fit it all in a small project box. The picture show everything built under the serial hood.

The bonus to this is everything is in the right there behind the computer. It's a very clean install, there are no wires outside the serial hood that you build it in. I didn't use this setup because the sensor is in the back of the computer.  I was worried about the line of sight from my remote and the sensor. Plus the IR module I used is rated at 40Khz, and general TV remotes work best at 38Khz. I really don't know enough information about IR Khz ratings and signal strength, So I don't I don't know if the 2Khz makes a difference.

I decided to mount the sensor inside the case. The reason for this is a direct line of sight to the sensor. Therefore I needed a couple feet of wire so the sensor reached from the back serial port, through an small hole I drilled in the back of the case, to the front of the computer.