I was wanting to change the rear gears on my 87 mustang, automatic transmission. Currently I have 2.73 gears, and I want something that is good for the street and the highway, because I would still like to do long distance highway driving. Back in the 90s when my uncle still owned the car he had 3.73 gears and said the RPM's were just to high for highway driving, so he had 2.73's put back in the car. I was wondering if 3.55's would be good for highway driving. Currently when I'm driving about 75mph in overdrive I'll usually be around 2100 rpm's just cruising.