well in my 98 I had 2.73s lol that was the stock gear , and then i went to a 3.73 .. me personally i dont tell a difference right now .. maybe when i get tuned i will ...
You have 3.08's. I went from 3.08 to a 3.73 and like the difference a lot. Definitely worth it if you find a good labor price and you plan on doing mods down the line, cuz up top a NPI stang isn't the greatest in stock trim.
I enjoy my 3.73s overall more than the automatic with 4.10s of which I have driven. Some guys in the city will say not to fear the gear, though the 3.73s fit my setup perfectly for the strip and I have nothing but good things to say about them.
Find an installer that knows what he is doing or you could end up with gear whine.