Electrical question

[76Blue_Beast]

I have a question that has to do with electrical work I'm trying to get done on my 76 c20 350/350. So, I had posted previously about HID's and about an engine harness I had to purchase and did. Now I had gone to the junk yard to get the bulkhead to the fuse box at the firewall on the engine bay side. As I was looking I had noticed it was looking fried from the short that created the harness to melt for lights and engine harness. I got a newer used one from another 76 at the yard and now I'm puzzled on how im going to plce the new harness pig tails into the bulkhead. It has this black gunk aroung the base of the bulkhead and the wires. Im not sure what this stuff is but figure it is for some sort of water proofing or making a barrier to prevent water from coming through. I also noticed grease on the other side which I'm sure is needed for this electrical work. What is this harder stuff and where do I get it? How do I remove it in order to get a clean area to replace the stuff? Iff anyone knows where I can puchase a new one that would be great too? I really don't know what the correct name is to this part either. It has stumped people.