Hi temp RTV (red). You put a bead of the RTV around the ports (either head or header) , assemble them FINGER TIGHT ONLY, let set for 24hrs , THEN you torque to spec. Works every time.
84 Cougar, 90 HO with 700DP, Edelbrock RPM intake, 1.7 RRs, shorty's and SS exh, T-5, KC clutch, Hurst pro billet, line loc, 8.8, 4.10s, suspension mods....blah, blah,blah.
71 Comet, 289, Liberty TL, 9", 6.00s, 11.9x @ 112.... blah, blah, blah