Being a MiniTrucker myself, and having my own S-10 that lays rocker panel, I have thought about a rocker dragging G-body myself.
First to get them rails laying down you would have to notch the frame. If you wanted to go to the rockers, like suggested by someone else, you could shave a little by fabricating your own body mounts, but there is limited frame to floor board clearance issues that would only allow a minimal amount of height to be eliminated.
If someone really wanted to drag rocker, I feel the easiest way would probably be to basically only use the stock frame horns from the firewall forward, then fabricate the rest from the firewall back.t Then by being designed with a lower profile and rear suspension configuration would create that stock floor body drop. One could use cro-moly tubing to drastically reduce weight as well. It's actually a pretty common thing in MiniTruckin Mag(if you want to see some very SICK chassis, take a look through one).