3rd Generation Sub-Frame Connectors
I've done quite a bit of research into SFC's for our lovely 3rd gen. F-bods, calling all the different manufacturers, private email with guys on the list with different SFC's, looking underneath my car to make sense of it all, thinking about it, etc. After all this, I have decided to get the South Side Machine connectors. They are only $127, not powdercoated (so I can paint them any color myself after the welding is done), are made of 2 1/2" X 1 1/2" X .120" rectangular tubing, and weld to the front subframe, along the length of the rocker panels, and to the control arm mounting points in back.
The feature I liked most was the way they stiffen up the whole side of the car along the rocker panels. No other SFC that I know of does this at such a good price. The MAC's were cheaper and powdercoated, but only attach to the front and rear subframes with a flat plate (see ads in CHP). The Pro Chassis ones could be bolted in first then welded, were $150, and powdercoated, and wrap around the subframes in front and back (see ads in CHP, Hot Rod, and other mags). The Global West ones are $180 and they couldn't guarantee they'd fit with 3-inch exhaust, aftermarket Y-pipes, etc. All the others had no problem with fitment (according to the manufacturers).
You could have a set made up from stock steel (either round or rectangular tubing and have them welded from front to back along the rocker panels and connecting to the subframes. That would take a lot of welding and trial-and-error fitting though.