PJG56 is right. If you have one of the 700's that has 23/27 in "3rd", your total drive ratio is 5.179. Which is close, but an average for GP is 4.75-5.0:1 overall drive ratio. If you had 25/25 gearset, your total drive ratio would be 4.4118:1. That would mean you need to be somewhere in between those two numbers.
I am curious to know what the transmission's assembly number is? We might can help you with what gears you have. Next bet, which I would recommend anyway, is to split the case and count teeth. Some transmissions didn't have the 25/25 set at all, and some had the 25/25 gearset in 5th. There are literally hundreds of combinations.