88 D 100 electrical issue

Where have you checked for power? I am not familiar with harness routing in these. Are both the front and rear parking lights out? It's possible the routing is ........from headlight switch.........to kick panel connector........branch off to front. In that case a break/ damage at the kick panel connector (example) would kill all of them

Have you checked that the tail/ parking fuse IS ACTUALLY supplying power under load?