Heater Box Help.

[quick60]

I took my heater box off the firewall today and have several concerns/questions.

1. The area on the inside (see pic) is badly rusted along the bottom. Very thin sheet metal to begin with. Are there any repair or aftermarket replacement parts for this. I looked at LMC and found nothing.

2. There was a thick layer of some type of black gooey caulk that sealed the box to the firewall. When I replace this what should I use to reseal it?

3. The interior heater box duct was rusted as well. Any aftermarket replacements for this box as well?

4. Is the rubber boot around the fan duct inlet available anywhere?

Thanks!!!!