[LS short box]

A number of years ago I mini-tubbed a 67 Nova. I thought the offset shackles looked a little weird. The local dirt track stock car chassis builder talked me into the sliders and they worked great. I forget which springs I used. I did use his double adjustable shocks. I had drove the car for about 4 years and then sold it to make room for a new project.
Can't speak to the load capability. That will depend on the rear springs.