[Advice Needed] 1,000,000 mile Truck with cracked block... to rebuild or drop-in?

Hi All,

Forewarning: very green to the trucking industry and made some expensive mistakes. Please bear with my ignorance. Seeking your advice / expertise / wisdom on a path forward.

Story:

• Family friends have a fleet of 15 trucks and offered us an opportunity to join their business. We accepted.
  
• Recently purchased a truck with a "rebuilt" engine... 13' Kenworth T660, Cummins ISX 15L 485 hp, 18 speed with a 86" studio sleeper and just a hair over 1,000,000 miles on the odometer. Beautiful on the outside at least. It's run for about 20,000 miles so far with a rebuilt head, liners and pistons. This truck was owned by one of their drivers and was recommended to us. In hindsight, we would never have purchased it for the price we paid.... probably overpaid by at least $10K and still have ~$18K in debt... yes, its bad.
  
• Details are somewhat vague, here's what is known: Driver was going down a steep descent (8 degrees) in Colorado, hauling a 48klb load when the RPM's shot up dramatically - he was in too high of a gear (7 or 8) when he started the descent and apparently the engine break was weak... next thing he knew there was a loud kaboom and the engine shutoff.
  
• Assessing the damage, there is a hole in the block - suspect that we threw a rod although am not sure quite frankly what happened. The truck is currently being towed back by one of our other trucks... during the tow, that truck also broke down.... Have not had a chance to fully debrief with the driver and visually inspect condition of the engine.
• Background: typically make runs from Houston to North Dakota, Wyoming, Colorado etc on Flatbeds. Severely lacking expertise on the maintenance side...

Goal: to get engine to a condition with the highest probability of operating for at least 3 yrs without a critical engine failure, without spending $30K on a brand new drop-in Cummins.

Questions:

1. Is something like this largely the fault of the driver or is it likely a poorly rebuilt engine? If not enough info, what other relevant details are needed to make an assessment? i.e. if you are the detective, what is needed to solve this case and identify root cause.
2. What would you do to fix this and why? Are we setting ourselves up for failure if we rebuild? Or would you go with a brand new or reman'd drop-in?
3. If you rebuild, what components would you absolutely replace without question? Which one's should be checked / depend on condition before making replacement determination?
4. If you go with a drop-in, any advice on selecting an good candidate? Concerned that we'd pick another bad engine that could blow up on us again.
5. There's an option to go with an old Detroit 60 12.7L... but that would mean changing out wiring harness, etc etc to make it compatibile... this feels like a mistake but would be a cheaper option. Also believe this violates emissions regulations.
   
6. Any recommendations on trusted mechanics in the Houston area?

Thank you for your help. Completely aware that are in over our heads - this has been a valuable lesson and we're trying to find the best way forward. Appreciate if we could focus on the situation at hand and spare any comments about ignorance or stupidity - we know we are idiots! If you have any other advice, please feel free to share.

 

Thanks for taking this seriously and for the feedback & sentiment. We are learning and moving forward!

To be clear, we were testing whether to replace the block, head, crankshaft, etc with aftermarket or OEM components keeping all other kit the same (EGR, Turbo, etc) - sounds like this is a mistake.

If the above is a bad option, would you recommend a drop-in? Concerned that if we go new, we're throwing $35K at a truck that would barely be even worth that much... and if we go used, that we'd risk repeating the same issue and throwing away $15K.

We've contacted Performance Kenworth in Houston and they quoted ~$35K for a brand new ISX drop-in.... any other alternatives?

Last thing we want is to throw good money after bad....

Really appreciate your help.

 

Thank y'all again for the feedback... Aligning on a used, reman drop in.

Any idea on where to find a good, used ISX15 with low miles? Looking online and they are scattered across the U.S...
We are located in Houston - not sure on the best way to source a used drop-in... concerned about quality / reliability.

Would you go with the 13' ISX or can we go with something newer? Are there an alternative engine model compatible with the 13' T660 that would be worth considering?

Really appreciate it.