Gears & Axles - What gears do i have?

I have a 1999 TA A4. The guy I bought the car from had the rearend replaced by a local shop, and has no idea what gears they used. I was told that you can tell what gears you have by your mph at 2000rpm's. Also, i heard wheels and tires can be a factor, so...

I have 17's in the front and 18's in the rear. tires are 275/40/17 and 295/35/18.

On the freeway under normal acceleration, i reach 2000rpm's right at about 70mph. Any idea what gear i have?

http://www.f-body.org/gears/

HERE.. (http://www.ls1tech.com/forums/texas-members/1259807-what-gears-do-i-have.html)

http://www.f-body.org/gears/

according to that, with my rear wheel size, i should be at 69mph at 2000 rpm to have 3.23s. i guess that's what i have. well that's good news. i don't need a spacer to go up to 3.73s.