keep us posted, I test drove a '99 that shifted in and out of OD on its own on the highway, didnt buy it, also had a 53 block. Ive heard some do some mod to the negative terminal, there is also some electrical thing you can put on it, search the cummins forums.
The dodge auto trans isnt known to live super long, typically. I try not to abuse mine too much, its still work good.
Ill have to try that trick posted.