I saw a as best as I can remember a 65-67 impala for sale in a used car lot in about 1977 or 8. The intake manifold and the valve covers were welded on.
I guess if the guy who did it got a good bead all away around you wouldn't have to worry about a vacuum leak or leaky valve covers ever again Ha Ha
I had a '68 Chevelle back in the day, never could get the valve cover gaskets to quit leaking................
