Picked up a battery today for my 89 pickup, and stupidly just hooked it up without thinking and put the terminals on backwards. Now the truck wont start and the radio and clock are dead. the dome light and headlights are still operational. I have checked every fuse i know of, and still having no luck. Hoping someone here may be able to shed some light on what i did and how to fix it. Thank you in advance for any help you may have to offer here.

 

There's a fusible link(wire) that goes from the positive terminal on the battery to the black 80 amp in the fuse block sitting nearby.
I'd take a hard look at that wire. It looks like regular stranded wire, but is designed to operate like a fuse. It might have one of those loose plastic sleeves protecting it. Look for heat discoloration and/or evidence of melting. Or just ohms check it.
If you need to remove the wire you have to loosen the fuse block enough so you can access the underside. It bolts in. Same with the black 80 amp it attaches to.
I've seen people cut out the bad section and butt connector it back together, but replacing the wire would be best.