I know the 6.1 has a roughly .20 or .30 bigger bore than a 5.7 and people talk about more wall thickness in the 5.7. However, I've never seen anyone claim just how thick the walls are in either engine. For all anyone knows, the 6.1 still has thicker, or as thick walls even after the final bore. Maybe it was designed with thicker walls than the 5.7 so it could be bored bigger and still have plenty of wall thickness. Not saying any of this is so, just don't know either way and I've never seen anyone confirm it.
On the other hand, I DO have Chrysler literature that states the 6.1 is beefed more than the 5.7 for the extra power and expected abuse.
* OK, I'd have to dig out the literature, as it may or may not say anything about "expected abuse". That's more just me throwing that in! lolol