I thought the Iveco marine diesels (FPT) had the best power curve when I was digging deep...but that was about a dozen years ago.
The thing is, the Iveco brand was selling for about 20% less than the Cats. So, that's a lot of $ for a different name badge stuck on there. Yeah, I know there are some differences and service, etc etc. But still.....it's even called "C13" in the Iveco lineup. The C13-770s are where I'd look first for my 52C if disaster strikes.
https://www.dieselmarine.com/Fpt-Iveco/Fpt-Iveco.cfm