Special thanks to JupiterBandit for helping me out with welding and fitment issues and to Elz for helping me out with alllllllllll sorts of rust-proofing, base-coating, and top-coating questions. I wanted to be sure I got the painting and sealing portion right so as to prevent this extensive job of replacing pans from ever being done again!
Couldn't have done this portion of the car without your guys' knowledge. Thanks for all the other info and advice the rest of you have offered as well.
Next up are the doors. I'm going to remove them from the car, clean them out, re-grease window tracks, properly align windows in doors, repair hinges (new bushings), and do anything else to them that I see fit. Then, after the interior is all reinstalled I suppose re-doing and prettying-up the rear end comes next!