Your car came with either a 2.79:1, or 2.80:1 rear end.  Autos may have come with 3.00s..  - Yes they had all 3.  What you have now, no one can tell off hand.  the gears easily could have been changed on these intervening years.

I bought a "C" code 3 speed - same engine as yours.
How to determine what you have now?  there are at least 2 easy ones that I know of.  
The rear axle came from the factory with a metal tag on the diff with the ratio stamped on it.
Or, you can put the car on jack stands in neutral and climb under it. mark the bottom of one tire with a crayon or something else that you can see readily.  Mark the bottom of the drive shaft.  Then turn the drive shaft and see how many turns it needs to turn the tire one revolution.  It is not exact, but there are ways to interpret it.  Less than 3 turns and you have a 2.79 or 2.80.  3 turns is a 3.00.  Something like 3 1/4 turns give a 3.25.  3 1/2 turns is a 3.55(or possibly 3.40 again they are close enough for your purposes).  Anything more than that will give you high enough ratio that you should know already that the engine is revving too high.  When I changed out my 2.79 for a 3.25 my gas mileage dropped from 19mpg to 16mpg.  I loved the added power and the way the car drove that way, but I was driving 30-40k miles each year and could not afford the extra cost of gas, so I went back.

There have been many discussions of rear end ratios here.  Advice is all over the place because we all do it differently.  But if you want a daily driver type of car, then stick with 3.00s or 3.25's for best mileage.

Be careful of "this guy got that mileage so I should get that mileage".  Mileage is a weird thing, because it depends so much more on HOW you drive, not how the car is set up.  For example, at what road speed are you computing mileage?  How was traffic?  How many times did you have to slow down or stop and then accelerate back to speed again?  How fast were you accelerating?  The harder you run the car the worse the mileage, regardless of setup.

Thanks everyone. I am aware of the how I drive part. I am slow smooth starts, steady throttle on cruising ( I have road with people that cant seam to keep there speed consistent  ever)  and I break easy. So I should get pretty good mileage. Just wondered if there was a taller set of gears to add a little more out on the highway, but it sounds like there may not be.