I built mine with two pull-up bars, one standard 1.25" and a fat one at 2"; I just used pipe as the supports on the top of the cage.
I made my rack 8' high on the inside, which is at least 6" taller than I needed; I would make my rack 7'6" if I were to do it again. I made my rack extra deep, as I really like having plenty of room in the rack; the disadvantage is that I am more likely to kink the pins if I drop a squat; but making new pins is no big deal, and I have not had to do it yet.
I copied the design for hooks off of a standard commercial rack.
Overall I enjoyed making my rack, but it took a lot of time. All of the racks I found commercially available were made from tube for the uprights. I wanted mine made with channel for the uprights so I could zinc all sides and prevent the rack from rusting because I keep it outdoors.