Wow deja vu. Been there with my 67 cuda build a couple years ago. Couldent afford a new floor pan, and my torsion bar crossmember had been hacked thru by a.careless previous owner. I used a clean crossmember, and clean used floorpan from a 74 dart 4 door. All the spotweld cutting you had to do X2. Awesome job so far on the duster.
Do you have pix of the XV radiator support. I bought a tubular dillinger bar for the lower support on mine to tie the framerails together. I used 2x3" by 1/8" thick square stock for my subframe connectors, layed it sideways. Did mine similar to bigblockdart.com. Cost me about $25 in materials.strong as hell. Naybe can save you some money over the cartool pieces.
Matt