'70 Duster - First MOPAR Build

I have a numbers matching really nice 67 Cuda. 318/904/7.25,,,But it's not staying that way. Dunno if I'm goin 451,408 or even LS 6.2. I'd keep everything to put it back stock as should you,imo. I'd consider a 340 6pac but these 340 guys think their gold. NOT.....