It really comes down to maintainence although engineering has a lot to do with it as well, if properly maintained 200,000 should be easy with any Mopar , Mopar had the best engineering with better rod ratios , harder blocks , better valve train etc. so the chance of catastrophic failure is less & as long as the engine is used within it`s limitations & not abused it will last a long time. I bought a 68 300 with 175,000 miles & the rear springs were rusted through the rear floor but it was the original owner & the engine was perfectly maintained & it still ran great & was spotless inside !!
Under using an engine or abusing an engine will hurt it , over reving will break parts although it is amazing what they will take & putting around & never fully working or heating the engine will cause damage as well
