Physically the 88 and on caliper should fit the 86 and 87 SEL. If you do this you should replace them in pairs since 88 and on can be Bendix or ATE and 88 and on appear to have a piston diameter of 40mm instead of 38mm. Mercedes has always been very particular about their brake balance so I am sure the difference in piston size made a difference or they wouldn't have made the change. If you do use the later version switch sides to keep the bleed screw as installed oriented upwards. Mark