quite simply, a standard automotive gasser doesn't have a duty cycle rating, as it wasn't designed to live in a 13k - 23k lb application. to live in the medium duty world, an engine has to exert at or near max power outputs for a large portion of it's lifetime. basically, the longer that an engine puts out higher power levels is indirectly proportional to it's service life.
a couple examples:
- marine diesel engines are typically spec'd at various duty cycles: 60, 80, and 100 %. as the duty cycles increase, rated power decreases.
- further example of above, marine 6bta Cummins peaks at 370hp rating, but may go as low as 210 at the duty cycle increases.
- when the ford 6.0 powerstroke came out, it was rated at 325hp in the pickups but the vt365 (same engine) used in International medium duty apps was rated at 235hp.
basically, you could get a small block to do it, but as stated before it was drive quite different because of the power band differences - gassers don't have as much "area under the curve" as diesels which represents total power output. and it won't have a high service life before reliability problems or requires a rebuild.
an industrial gasser is designed to live in the MD world - a fair comparison, crack open a 300ci Ford straight 6 and compare the internals and block thickness to the deuce gasser. the deuce gasser will look like a diesel compared to the Ford.
lasly, a big block will help regain some of the area under the curve, but won't be equal to a diesel. also, since it's easier to make the same power with more cubic inches, it was have a longer service life than a small block, but still not as high as a diesel.
not sure what all they did to the trans but it was a good enough starting point for them to use it
