While installing headresrs on my 1968 250 SL which was manufactured in December of 1967 I encountered a problem. The grommet size changed during 1968 I think. Early they were round then as the 280 was released in later 1968 they become oblong. Oblong grommets will not fit in earlier seat frame designs. They sit too high protriding over a quarter inch above seat top. My seat guy is now trying to cut them down to fit properly. Old style round ones are available but only in black and $ 18 bucks each. My headrests are the newer style that move forward and back so round grommets will not allow movement. If you do this conversion be sure your parts are from the exact same style headrests and frames. Live and learn I guess!