If your engines need rebuilding, these guys offer overhaul
kits and rebuilt parts
for your engine
Cummins Engine Parts | V6 | 378 | V8 | 504 | 555 | 903
Also Ebay usually has people selling new and used parts. And there are many others.
My rebuilt mains are 68 years old and will outlive me.
I've always found it much cheaper to rebuild
than replace. Even cheaper if you can do the work. Often mechanics have their favorite brand and everything else is crap - in their mind. Many 'comfortable' yacht owners think everything has to be brand new. Don't get caught up in that thinking.
Cummings builds good engines. Properly rebuilt should last as long as new and can be rebuilt over and over for many years. What hurts turbo engines is the higher exhaust
gas temperatures that eat away at the rings, sleeves and valves. Keep the rpms down and you can double the life between overhauls. And maintain clean oil