I fitted 1984 300SD seats in my 1976 w115, i found they fit almost perfect, just need to drill two holes per seat. I havent permanently installed them yet, need to get them reupholstered as they don’t match color. Reason I wanted them was I don’t like the spin knob to make the seat back recline, I’d rather have power. I found there is room on the center console to install the seat controls, rather than the door panel. This makes it easier to run wires and lessens the likelihood of wire breakage as it’s not constantly bending everytime the door opens. I robbed the wire harness from the donor car too, so all I need to do is connect connectors, and supply power and ground. So thats my seat story.