Old school . Back in 67, If the heads and intake are milled to fit .the ports in heads, manifold, and gasket all line up and the top valvecover gasket rail is one flat almost even ring. The two small top gasket tabs protruding from the intake manifold to head joint on each head are carefully peened over , that has allways worked for me. I used
oil resistant RTV. clean valvecover gasket surface with something like braekclean. I glue the valvecover gaskets and cover together like I was never going to remove them ( you want the gasket to stay with the cover), bolts can be used to keep everything in place . after some setup time I place a thin layer on the gaskets let skin over the I mount the valvecovers and lightley tighten the bolts. After letiing the TRV set up I can evenly snug the valvecover bolts a little more and run the engine to see If I have been scccessfull.
The red or orange RTV is a higher temp than blue RTV both are
oil resistant. The red or orange also set quicker than the blue.