Exactly what type of use did you have in mind? Honestly that'll be the biggest deciding factor on type of suspension. The two most common on sand rails is the VW torsion beam, and the long travel a-arm style. If you'll be doing simple dirt road driving the torsion beam would work fine, IMO it's be more than enough for mild offroading as well. If you'll be driving and jumping it like they do in the dunes you'll probably want to build a long travel suspension.
For what I have in mind, I'd using the torsion beam. Most of my off road use would be on rough dirt roads, logging roads, and skidder roads. Got no interest in, or desire to jump any vehicle. Sure high speed over rough terrain would be fun, but we don't really have areas open enough for that around here. If the torsion beam handles what the military uses it for well enough than I think it'll work fine for me.
EDIT: Guess I didn't really answer your question. The #1 donor for a dune buggy suspension would be an old VW Beetle, the standard beetle not the super beetle. It's actually convenient because if you plan to use a transaxle that is also the #1 donor of them (though a bus axle might be better for that motor, really not sure). Other than that I'm really not sure. It depends on your designs and, as mentioned above, what you plan to use it for. If it's going to be primarily off-road you might even want to think about the front suspension from a larger 2wd 4 wheeler.