The military 6V53T in the latest version puts out 400HP. A factory marine 6V53TTI can also make 400HP with the correct injectors. This is not to say all 6V53's will make 400, only with the proper equipment. I have not seen a spec sheet for a higher HP 6V53, if it exist.
Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-