Truck was running, but when you turn key over no power to anything!

No horn or brake lights either. Battery has full charge. It's a 1989 instead of a 1990 also.

Check your ground(s) and positive cable again , then start from positive terminal at main underhood fuse box and test for voltage you will most likely find a blown 'main'(100 amp or near) fuse. Key will be to trace the power to where it stops.