Help with power decision

If your rear end is good you could transfer it over to a low mile single axle truck. Would involve frame work but single axles are cheap

 

The DDEC 2 engines are actually a good engine. If all you need is a bull nose gear, I would fix that. If you wanted to upgrade to DDEC IV you can go get another ECM off a wrecked truck. They are very easy to find online. Than I would get a Mawk Harness. He really knows his stuff, and if you have any questions he can walk you right through it. He builds a very nice product.

Personally I would just run the DDEC II, and buy a Launch HD scanner. It will read your DDEC 2, and they only run about 125.00 off the web. I use the same scanner for all of my trucks. It works great on everything I have hooked it up to. Have to switch the protocols sometimes to read the engine codes, than the brake codes, but all in all, great little tool.
i put a review with pictures in here on the Launch. Fix the motor, and run it, but that is just me. I also do my own engine work, so my cost are way different from taking it to a shop.

Good luck which ever way you chose to go, If you do go back to a Cummins, make sure it is a BC3 or BC2 and not a BC4. I was never a believer in the low flow cooling, they have given many a headache. If you do go to a BC4 you will need to mod the cooling system for your current set up as the Detroit uses full flow as do the BC3 and BC2.