4.30 gears are way low for street driving. Drag racing, road racing with short straights and heavy towing, yes. For street the 3.55 gears are a good choice especially with an OD trans with a lower 1st gear ratio. The GM 700R4/4L60 or the Ford 4R70W come to mind.
These days the OEMs for trucks intended for towing install minimum 3.73 gears with 3.91 to 4.1 more likely. The highest tow ratings option 4.3 gears. If you tow only for holidays or drag the RV out to the lake lot in the spring and home in the fall, less gear is probably a better choice and downshift the trans manually. You will use way less fuel the rest of the year, and fuel economy when towing is never stellar. Now a work truck that tows regularly is different, get the gears.
A race car is different than a street car in a similar manner, intended use and the balance between street and track miles put on. If your intent is a snappy street driver for cars and coffee tours, 3.55 or 3.73 gears and an OD trans is the way to go.
Another consideration with gearing is the tendency to gear noise or whine. Some combinations are more prone to noise than others. The Cartech Books Ford Differentials has a list that shows which are more prone to noise and which tend to be quieter and why. 3.55 and 3.73 are better ratios than 3.5 and 3.7 in this respect. 3.89 or 3.91 should be quieter than 3.9. Ratios mentioned may be manufacturer specific.
