I did it in my 77 440 truck. Like it a lot. I used the PATC vacuum and pressure switch set up also. Mine is a lock up version and I installed a cut off switch on the dash. Went from 10 mpg on the interstate to a best of 14.4 mpg running 75-80 mph on the interstate. Only negative I will say is pulling large hills or getting up to speed on a hill it kicks in and out and in and out. I have just got to the point where when I know it is going to do it a lot I turn overdrive off till I get past that point. But cruising with the overdrive and lock up is nice truck sounds like it is barely up off idle. My tach doesn't work so I can't give you a real RPM difference number. Any questions ask away it has been a while since I installed it probably about 10 years and will do it all over again on the 78 I'm working on.