Thanks! Other than the tunnel, its pretty easy with the ToddRon Restorations crossmember kit. Looking back at it, I also really appreciated he Hurst tunnel patch since it was pretty close to the right shape to start, and it was also 18 gauge which seemed to match the original floor, and isn't easy to find (most places seem to have 22 ga and 16 ga).
I do have to give the public service announcement that no, you will not install the crossmember with a 110V welder. I upgraded to a Millermatic 211 before starting. You could of course do the sheetmetal work with one.