i have a 1983 stang with a 1993 interior. the fuel gauge used to read backwards [tank was full, gauge read empty, it wood move up 2 lines til it was emoty] installed a 93 tank with a 93 sending unit. it reads full when tank is half. 2ND ISSUE IS THE KEY, WHEN I TURN THE KEY IT SPARKS 1/2 TURN AND NOT FULL TURN. HAVE NEW KEY CYLINDER AND SWITCH.I ALSO REPLACED THE STEERING COLUMN.
PLEASE HELP