Sorry, it's not a bolt-on exactly, but I took a plate of like 1/4" 'hard' aluminum plate and cut a ring out of it, that slid over the oem valve cover, and over some studs I put in the tapped v. cover bolt holes. It acts like a big girdle, putting even clamping pressure on the cover & gasket, and TOTALLY stopped all the leaks on my 400ci 76 w200. It was kind of a hassle to create, but I was SO tired of smelling burning oil and ruined gaskets. I must have tried a half dozen different gasket designs. I even tried new exhaust gaskets with integral heat shields to keep the heat from cooking the outside bead of the v. cover gaskets. Nothing worked, until I came up with that fix.
