Fuse box problems on 1977 and 1978 Mopars

I'm sure you are on the right track........corroded, lost temper on the fuse holder. Or loose rivets. Some of those are one piece, that is, the load side clip and the wire terminal are all one piece. Of course it could be in the wire termination as well. "It's right there" where you are now.

Get some "No corrode" (spelling?) soldering flux, clean it up good and solder it together. at the clip.