ECM or not

[murph]

[/B]I have a 1992 Dodge 2500 4x4 that keeps shifting w/ a rise and fall in rpm. It has a new transmission in it and has been apart 2x's. I was wondering if anyone has had this problem before I go ahead and replace this ECM unit. Can anyone recommend a company to buy one from if I need it? I thought we had a mechanical problem with the transmission and have had it rebuilt (its a 47RE) . At around 50 MPH the tork converter seems to unlock and the transmission shifts up and down like it can't decide where to be. We have replaced the TPS and virtually every other sensor. The transmission was completely overhauled and a diesel billet converter was replaced. It seems to be something electrical because it may not do it for 100 miles or may do it non-stop. We bought the truck with 170K and don't know the complete history on it. The only thing I haven't changed is the ECM and I'm wondering if this is possibility? The reason I'm asking is the local garage hooked the scanner up and wouldn't talk with there scanner or give a data stream, it all came up NA? If this could be the problem, where would be the best place to get one reasonable? I don't want to throw parts, but I want to get it fixed.