rear coil-overs

[chigger]

Though I wasn't looking for them, both the Koni and Bilstein sites had coil over shocks. Look under the hot rod headings. They had different length shocks and different springs so you could get together a combination you could use. The stock car sites have lots of infor on springs and spring rates as most of them sell the parts.
I hope you are going to save the trailing arms and flex plates it would make things easier. A buggy with a mid engine uses custom arms which might be affordable.