Now I'm leaning towards the later 2012 66RFE automatic trans, as long as it will bolt up to the 4.7. The 66RFE has a slightly higher 1st gear ratio, 3.23 versus 3.0 for the 545RFE and 65RFE. That gets it closer to the 3.55 1st gear ratio I'm familiar with in the 5-speed manual in my donor Dakota chassis. Also, the 66RFE allows me to manually shift to 2nd for lower traction takeoff in the winter on slippery surfaces. It takes over automatic shifting above 25 mph which would be about right anyway. And the 66RFE has a 0.62 to1 6th gear overdrive. With the tires I plan to run, and the 3.55 final ratio in the 9-1/4 rear axle, I should be turning real close to 1950 rpm at 75 mph on the highway for decent fuel economy. Mostly flat and rolling roads around east central WI so I think 20+ mpg is possible. The 66RFE can certainly handle the torque of a modded 4.7HO (intake, exhaust, cold air intake, etc).