. . . in that it represented the very last legitimately high-output engine from Dearborn during the original muscle-car era. The '72 H O 351 Cleveland, an option available to Mach 1 buyers, still had high compression and aggressive cam specs. Mopar dropped every high-output engine in '72 (save for a handful of 440 Six Packs produced early in the run). GM actually introduced one in '73, the Pontiac 455 H O, but that lasted only two years (dropped after '74).
That '68 Plymouth Fury convertible would be my pick of this lot, though.
Art