[tdangle]

You will also need to add 3-400 RPM for converter slippage to those charts. My C20 with 4.10 and TH350 seemed always to be 3000 + on the highway. While that's what the motor did when it was new, We have all gotten use to OD 2-2200 RPM cruise on the hwy, not to mention the noise factor. I went with a 4 speed OD auto trans, best of both worlds and did pick up a few MPG.