Are your RPM and MPH numbers from the tachometer and speedometer in the car? It's a bit dicey to back calculate from these numbers if that is the case, as neither the tachometer nor the speedometer are particularly accurate.Trying to figure out the gearing of my X. If I'm turning at 3500 RPMs at 55 MPH, what final drive ratio do I have? From what I can determine, the options are 4.42, 4.08 and 3.76. To the best of my knowledge, I have a 74 tranny connected to a 74 1300 engine. Thanks.