Actually I have done three sets recently. I recommend cutting the old floor pans and factory frame rails out as a set and replacing them all with a better fitting, stronger design. Maybe we can do a special on that next month if I'm not to busy. You want to use a 2inch by three inch boxed steel and have it welded into the floors, but when you replace the floorpans with the rails it make it so much easier to line everything up and helps clean up the underside of the car.
Mike, have you actually done this to a ZX? Seems extreme, and it's the first I've heard of the procedure. I'd definitely be interested in hearing more when you get around to posting again, as the frame and front floor pans on my '82 are pretty mashed and dinged up.