I would measure the width of the rear axle from wheel mounting surface to wheel mounting surface. Seems to me that '88 was the year they changed the body styles(the pickups anyway) and they started using the wheels with a lot of offset(the center part of the wheel that is against the brake drums is almost all the way out to the outside edge of the wheel) This may mean that the axle assembly got wider. Easy to tell if it's too wide with the measuring tape. You will want to know the gear ratio of the axle also. It's probably pretty fast(which is what you want) but you will want to verify that before you spend your hard earned money.
