I've had so much help from this forum with my 98 4runner that I had to share a neat little trick to get those pesky back seat headrests stored when the back seats are folded away. You purchase a set of Flymic car seat headrest hooks from Amazon (
Amazon.com: Flymic Car Seat Headrest Hook, 4 Pack Car Storage Headrest Hanger Holder Hooks Organizer, Universal Vehicle Strong and Durable Backseat Hanger Interior Accessories for Handbag Purse and Bag Black : Everything Else) for about 8 bucks. The hook needs to be wide enough to accommodate the diameter of the headrest support. You then drill a 7/16 inch hole centered in each hook. Be sure to start with a smaller drill and move up to the 7/16 inch one to make a nice round hole. Then install the hooks and slide the headrest supports in each hook. That's it. I've provided pictures below to show how it looks. The hooks give good support to the headrest and when not in use make a great way to hang stuff from the back of your seats as they were intended.