I don't like the use of air shocks. They put unnecessary strain on the weak upper sheet metal shock mount. Seen a few uppers broken badly and even a few lower ones broken. My bought new yellow 74 Hornet came with a 4 leaf rear spring. My bought 7 years ago orange 74 came with 3 leaf rear springs that were badly sagging and the owner added lifting shackles which did nothing. I bought a set of new heavy duty springs with new stock shackles and bushings from ESPO. I also added a set of Monroe gas shocks. I haven't had a problem and am very happy with the results.
"Doc"