There should be a tag on the rear end. Or you can jack up the rear wheels and mark the drive shaft, and then spin the rear wheel one rotation and count the turns on the drive shaft. Example on turn on the wheel and 3 1/2 turns on the drive shaft will be around a 3:50 ratio.
1969 Mach1 428 4-speed 3:89 gears,
31 spline posi "N" case, ported edelbrock heads,
full length headers, 292H Comp cam, 750 holley.
Born July 17, 1969
2002 SVT Lightning, Supercharged
1959 Alfa Romeo Giulietta Spider Veloce