Gearing question

jack up the rear of your car and support it on jackstands. mark a rear tire with chalk,marker, ect and also make a mark on your driveline. count how many turns (by hand) of your driveline it takes to do one full rotation of your rear tire. this will tell you your ratio. 3.27:1, 3.55:1,3.73:1 ect. Charts can be deceiving as tire size differences aren't always accounted for. Hope this helps.
 
I would guess you have 3:73's...

What size tire you got?

Smaller than stock tire, you could have 3.90's.

Bigger (taller) than stock tire, you could have 3.55's.

Ballpark, you probably have 3.73's.