Got the 94-98 filler panel mounted in there, and used some spacers to adapt it to the 88-93 core support. I used 3/4" spacers on the ones shown, and a 1/2" one for the center. The far ends ones didn't end up on a flat spot on the core support. For the time being, I didn't attach those, and all seems sturdy. If I end up needing them, I will make a small bracket to attach them. After the grille clips in, it is firm.
Also cleaned up and re-did some wiring on the front lights. Got them all working, and did new bulbs and housings.