What vehicle produced by General Motors from 1962 to 2002 did testers feel was a more roadworthy car as compared to the Ford Thunderbird?
Ford Thunderbird (fourth generation): The fourth generation of the Ford Thunderbird is a large personal luxury car produced by Ford for the 1964 to 1966 model years. Ford Thunderbird (fourth generation):  Contemporary testers felt that the Buick Riviera and Pontiac Grand Prix were substantially more roadworthy cars, but the Thunderbird retained its leading market share. Pontiac Grand Prix: The Grand Prix was a line of automobiles produced by the Pontiac Division of General Motors from 1962 through 2002.
Pontiac Grand Prix