I've had the same question for a while now. I went from stock to 3.73s some years back when I had to replace the spider gears and posi unit. I run a 275/60/15 Nitto DR at the track or the MT ET drags in a 28x10. I've been trying to figure out if that's part of the reason my car won't run faster than 11.70 with the stock heads no matter how much boost I run.
They are fun on the street though
Lots of guys running WAY fast with stock ratio. To make a more educated guess, you would need to post your engine mods, turbo, trans mods, which trans, converter, tire size, how much boost you run, what are your plans/goals, etc, etc, etc. It seems a lot of guys who change gears then have to mess with tire height, etc. In my opinion, the only reason to change gear ratio is if you are not where you want to be RPM-wise at the end of the quarter mile. If you are dead set on a 29" tall slick, then maybe 3.73's are right. If you run a 26" tall tire, then 3.42's are good, etc, etc.