I've got a 94 with time delay interior lights...
I didnt have this problem, however the answer to my problem MAY lead you in the right direction...
As some one said above, check the tailgate lock mechanism as it may have the light switch incorperated into it...
My problem was with my after market alarm system. The tail gate would not trigger it when opened.... The sale rep/installer refused to accept it was not the tailgate switch. I knew it was not this as I pulled it out rebuilt it and tested it... FINE, nothing wring with it...
After two weeks of reading the manual and checking every thing I could, I found it was the 50cent switch in the dome light in the cargo area... BAD EARTH...