Updates...
I went to the local metal supplier and bought some more 1/8" sheet stock and some sections of 1", 3/16ths wall tubing from the scrap area. 37 lbs total at .79 per pound.
First job was tack weld the trans cross member nuts to the member so that I don't need a wrench anymore to install the bolts. I then straightened the frame rails where a floor jack had bent them up a little and prepped them for welding by grinding the surface rust off.
A design cue and one issue to deal with here- Notice I put the sheet stock in the brake to bend it slightly, matching the design cues from the front frame rails. Just a little added visual touch that only took a couple extra minutes.
Also the body mount area needed some working. It's curved at the top and you need to leave it open so you can get a body bushing up in there. After welding on the longer sections, I made the smaller body mount sections using the table mounted plasma cutter. Once they were tacked into place it was fairly easy to get them to contour to the curved upper rail.
I'll have the open gaps where the factory boxed rails meet mine boxed in tomoorow, and then it's on to building some bracing into the frame...