Here's...let's just have it done with.

M.A.N. That's their real name, Maschinenfabrik Augsburg-Nurenburg. I toured their factory (Augsburg Germany) back in the early '70s. They had a big 20,000+ hp ship engine down in a hole for testing. I asked if they had a dyno that big or how they verified h.p. German tour guide engineer said "no dyno". They measure the amount of fuel going in and compare it to the exhaust heat output & come up with h.p.

Take one of their big engines. You can get it in either 12, 14, 18, or 24 cylinders. Put that on the option list.

22,000 hp for the big one @ 500 rpm. Should keep the noise down in the cab. They're reversible (so ships can back up) also. Probably no need for a transmission....just a big differential.

https://marine.mandieselturbo.com/docs/default-source/shopwaredocuments/man-v48-60cr.pdf?sfvrsn=5