A/C from scratch for Classic Mini

I'd like to understand what I need to create an a/c set up for my '74 Mini. I want to be able to defog my car without using the fake version of turning up the heat.

I have seen a/c compressors (that fit my car) for sale on eBay, but I know there is more to it.

That being said, an active dehydration unit may be a great substitute.

Any thoughts?

Jerry