I put a bead of clear sealant around the bottom edge of mine. Let it dry for a few days before installing it on the hood.
The '68 I owned back in 1979 had an original hood tach and fitted gasket with a sloped edge. I do not believe anyone repops that gasket. And I have heard from others that '68's did not come with said gasket, but I had it in my hands many times, so I am convinced they came with them.
Sold that car a hundred years ago, so can't prove or disprove at this time. Never took pictures of stuff back then.
I used to be indecisive. Now I'm not sure. I feel like I am diagonally parked in a parallel universe. 1968 400 convertible (Scarlet) 1976 T/A - 455 LE (No Burt) 1976 T/A New baby, starting full restoration. 1968 350 - 4 speed 'vert - 400 clone (the Beast!) 1968 350 convertible - Wife's car now- 400 clone (Aleutian Blue) (Blue Angel) 2008 Durango - DD 2008 GXP - New one from NH is AWESOME! 2017 Durango Citadel - Modern is nice! HEMI is amazing! 1998 Silverado Z71 - Father-daughter project 1968 400 coupe - R/A clone (Blue Pearl) (sold) 1967 326 convertible - Sold 1980 T/A SE Bandit - Sold