Dom91

So I recently picked up a 91 pickup with the 3.0.
Been doing alot of work on her and finally got to installing the radio.. to discover both the radio and cig lighter fuse slots are completely melted can't put a new fuse in it's so melted.

My question is what caused 2 separate slots like this to melt and should I be looking for a new fuse block? Can I just get a aux fuse box like I already intended on getting one for other applications..
If I do just get a aux fuse block can I retain the stock fuction of the power to the the radio as in comes on when in acc but goes off with key in off position etc. Not very good at electrical..