What transmission do you have?
To determine what the car had originally, assuming the gear ratio has not been changed, you need to check the code stamped on the bottom of the diff itself.
THIS pic will show you where to look.
THIS pic will beak down the codes you see. It's the first two letters that tell us what ratio it has...or had originally. However....the gears may have been changed at some point in the vehicle's life, so the only way to know for sure what ratio it has is to remove it and check...unless you know the history of the car, and know it is original.
Find out what the code is, and then refer to the following:
AA= 3.55
AB= 3.70
AC= 4.11
AW= 3.08
AX or LR= 3.36
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Joel Adams
C3VR Lifetime Member #56
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"