Hi Ben,
1. Front supply and return A/C unit has been provided.
Front side of supply and return air of A/C unit has been provided.
2. Bottom return A/C unit has been provided.
Bottom side of return air of A/C unit has been provided
A box is usually considered to have a top, a bottom, a front, a back and two sides. So, it sounds odd to talk about 'the front side', just say 'the front'.
In these kind of technical sentences, we often don't put in the full English wording. We rely on the reader's technical knowledge. However, to try to make it much more complete English, I'd say something like this.
1. An A/C unit with an air supply and return in front has been provided.
2. An A/C unit with an air supply and return on the bottom has been provided.
What about the sexy kangaroos?
Best wishes, Clive