There might be slight differences in the seat belt. Most '91's, I believe, had shoulder belts in the rear, which took away the center retracting bits in the seat itself which non-shoulder belt models have. So if you get a seat from a shoulder belt model, youll have fixed length outer position sections in the center of your seat, and you '86 will have fixed length outer sections attached to the body itself, leaving you with no adjustment and 2 female ends for your outer position belts. Bolt up wise, it's a straight fit.