[King951]

So I installed a tachometer on my truck. 12V + tach wire off my HEI distributor. I also used a GPS speedometer to get a semi accurate reading of how fast I am going. At 60 MPH I was at 3,000 RPM. I used an online RPM calculator taking my tire size into account and it read my rear gear would be around 4.6 give or take a little. So I am pretty certain I have a 4.56 rear end. I do enjoy the pulling benefit of the 4.56 but going 55 MPH on the freeway gets old pretty quick. An overdrive sounds like a nice alternative. Using the same calculator and the fact that my new tires will be about 1 inch taller, if I had a standard overdrive I could cruise at 70 MPH around 2550 RPM which sounds much better. Only issue is an overdrive transmission conversion sounds like a big job. I found a local shop that sells rebuilt 700R4 transmissions for about $450 with a 2 year unlimited mileage warranty. Maybe one day. Thanks for all the feedback so far everyone.