3.55. I' run 3.55 on my 440 Cuda, 275/60/15s. More highway than city now that I've moved but it's still a great gear.

ANY rear gear is a compromise IF there is no overdrive and the car runs a mix of city and highway...period.

3.55 isn't perfect in town, and it isn't perfect on the freeway....it's just better at both (or doesn't suck as much if you are a glass half empty guy) than the others.