Plymouth trucks lasted into the mid 1940's
Fargo trucks last year was 1972 (first year of that body style), so you could find a tailgate form one of those that will fit all they way into the 1990'a, but good luck.
Trail duster/Ramcharger hatch is not a tailgate. You'd have to cut and weld.
Mercury trucks went into at least the mid 1960's.