The short answer is no, you can't convert normal shelving units into suitable habitats for Ball Pythons.

Your choices pretty much are:
1. Buy a rack specially designed for snakes
2. Build your own rack specially designed for snakes.

If you decided to buy one I would recommend Reptile Basics. I own 9 of their racks and I couldn't be happier with them. http://www.reptilebasics.com/reptile-rack-systems/