I have a friend with an '03 2500 commonrail that melted a piston because of bad injectors. The cheapest engine he can find is $2500 and we don't know what shape its in. He does have a p pumped 12 valve and since the blocks are similar could he make it fit and have the gauges and everything work like they should?

 

I am not an expert, but I do believe that they are two different engines.
Is his truck a manual or auto?
Of course, there is the legality- although it isn't very regulated, you aren't supposed to put older engines in newer vehicles. Engine replacements need to be at least the model year or newer, and meet the EPA standards for the year of the truck. I know in VA that isn't enforced, but it is a part of the equation.

 

You will have a hard time gettn the gauges to work. The 12v is a mechanical engine which doesnt have a ecm(computer) and the 03 has an ecm. The ecm gives the info to pcm (cab or oem computer) for gauges. I no people have done it but a lot of work.

 

The truck has an nv4500. Could the ecm be left in the truck and use the 3rd gen sensors on the older engine?

 

Thats what I would do. The 3rd gens use an engine speed sensor on a tone wheel on the balancer. 12v's were similar. You could most likely bolt a 3rd gen balancer to the 12v crank and use it to keep the 03 ECM happy. Then just adapt the rest of the sensors. You will likely lose cruise, since I think that was all electronic by that time. Might be able to rig up a vacuum system from a 2nd gen to control it, I have heard of that being done before.

 

the ony gauges that will work correctly is the temp gauge and the speedo. i did that conversion and unless you have lots of time its a pain. the tranny will mount up and so wiil the exhaust and one motor mount. all the other stuff has to be rigged borrowed or fabricated