The first thing I would do is hit all that rust with a wire wheel on a grinder and get all the flaky loose stuff off so you have a better understanding of where the good metal starts.
If you can weld the repair is quite manageable.
For the footwells out hosts sell replacement panels. I never figured out why they galvanized a footwell panel that gets welded in place though. Watch out for the galvy flue.
Have a good look at that mounting foot and see if you can get away with plating it.
Paint it with your favourite rust proofing coatings and you're done until you get that irresistable urge to galvanize everything.
Ike has a great description here:
Linky