I believe the "DH478" is a Toro Flow, based on the GMC V6 gas engines.

Don't worry about total cubic inches for Detroits, that's not how they are refered to. For eaxmple, a 6V53 is indede 318 cubic inches, one version of an 8V71 was 318 HP, see the confusion? Just stick to 6V53, 8V71, 6-71, and so on.
Another reason, with your total cubic inch logic how do you tell the difference between an inline and a V6 71 series?

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-