Dave,
I've got 3.73 with the same size as bpoche.. You're ST is REALLY going to have to work to get that size of tires moving with that gear ratio.... I wouldn't advise it, since mine right now with a 265/75R16 has to work pretty hard to accelerate with the gear 3.73 gear ratio...
If you want to see how much of a difference it makes click the link and put your tire sizes in. And if you need any more info, I can e-mail you a bunch more about the change out because there's MUCH more involved with the ST than just the tires when you go up in size.
Let me know.
~Josh