Sorry folks - but I had a reason for saying what I did -
A Gen 3 426 refers to the last series of crate 426 motors released by MP - at least that is the context Ive seen the term used in on both the LX and Moparts forums - .which is why I said advice would be limited.
If the OP means a stroked 6.1... Then obviously he's come to the right place :)