What is the sealant that is used between the AC box and the firewall? Real sticky black stuff..

3m Strip calk part 051135-08578

Ditto, bought a box yesterday. Installing the suitcase tommorrow.

Yes, Use a light in a dark area to see how well you are doing or have done. You won't need a lot, but more than you might think. You will also use this on the NUTS from inside the door on the bottom before you install the R/S Moldings nuts. Just wrap some around the studs and install the nuts.
Since the tail light bezels are not a perfect fit, you can use it to push from the inside to make sure water does not get in through the lights bezel, (the gaskets on these suck, too thin). No one will see if you do it correctly.

There are several places you can use it on the A/C plenum at cowl.

Kick panels are good also.

DON'T GIVE THE BOX AWAY. YOU WILL USE ALL OF IT.

Thanks.