My Hemi made 697hp on the engine dyno. I put a non lock-up 518 behind it by changing the bell housing. It has 3.91 gears. I did build it to the heavier V10 and diesel specs and with a custom forward manual valve body built by A&A. I also used the aftermarket heavier OD spring. I don't know if it was necessary, but it got it.

I have a manual button for the overdrive and an adjustable vacuum switch to drop it out under load, kinda like a passing gear. Been in there 3 years, and so far I have been very happy with it.