I'm addng headrests to my 77 warrior and want to know if headrest holders (receptacles shown in the parts manual) are needed. I haven't taken the front seats apart yet and don't know if the seats will accomodate the headrests. Reading several earlier posts, it appears that there are just holes drilled into the seat frames. Curious how the headrest stay in place. Any pics of a bare seat frame would be helpful. Thanks