The pre 1973 ( and subsequent models continued essentially unchanged) cars eligible for the Trans Am were basically limited to American Pony cars with 5 liter V8's.
Later Trans Am cars included Corvettes and other sports cars such as Porsche etc. were allowed much bigger engines ( 454 for the Corvette ) along with Jaguars V12.
Jaguar didn't get involved until 1978 and yet twice won the driver's championship and once won the mfg's Championship even though only 2 Jaguars were ever entered. One Jaguar ( and finally the older version entered to be driven by the mechanic ).
Winning in spite of being greatly outnumbered. Only developed by one team and giving away 125 cubic inches.
