Do you mean between the SRT-Ram's (and SRT-10 Viper's) 8.3L V10 engine, and the Gen II Viper V10? Or do you mean the difference between the RAM trucks iron block 8.0L V10 and the GenI/II Viper's V10?
The original iron 8.0L V10 truck engine was supposed to be the basis for the Viper's engine originally, and the Iron blocks were sent over to Lamborghini to cast into aluminum, and a new intake and valvetrain built by them.
At that time Chrysler owned Lamborghini, who had experience in aluminum foundry work, and of course in designing and building high performance engines.
But the Dodge engineers discovered that Lamborghini was more intereseted in building a high revving, high HP, lower torque engine, that was frankly not suitablly reliable for the Viper's intended use.
So the Dodge engineers did a clean-slate design, with no common parts between the truck's V10 engine and the Viper's, and only the intake manifold was kept from the Lamborghini design and engineering work done.
But that story is where the myth of the Viper's V10 engine being a truck engine was started, and why it's untrue.