Chevey,
I did get the trunk pan installed in one piece. Since I had to replace both rear quarters, I removed enough of the quarter panel to slide the trunk pan from the side and rear. Since then I've spot welded the new wheel tubs together and spot welded in place. Dimensionally everything lines up perfectly side to side, front to rear. I've already temporarily fitted the new quarter panels and now I will make my final cuts before I have to but weld a mile of joint haha. I did learn the best way, or at least I think it's the best way, is to use a pneumatic flange tool that creates a beveled edge for both edges that creates a valley between the edges so when I stitch weld the joint it provides more weld surface so when I grind down the weld I don't run the risk of the joint cracking. If you have a better idea I'm all ears
Perry