If the 5-speed's 5th was overdrive, I'd keep the 3.73's. Some aftermarket 5-speeds, like the Richmond, have a very low 1st gear, and no od. With one of those you could put a 3.07-3.50 rear gear for cruisin' and still have that hole shot....if your existing 4-speed is a close ratio unit, it'll have a fairly high low gear and won't be happy with less that a 3.73.
jmo,
Johnny