The engines (and peripherals, notably the cooling radiators) used on mainline diesels in North America are big enough that a hood covering them comes too close to the top of the loading gauge to allow much higher cabs. The Cat 3512 is a smaller, higher r.p.m., engine than the GE 7FDL-12 originally used on these units. (Note that the power has been reduced to 1550 kw: the units were originally built as something over 2200 kw.) So this rebuild is perhaps comparable to the "genset" switcher/local freight units built in the past decade or so, using small-bore, high-speed, diesels. (Some have been built on the frames, and with the trucks and fuel tanks, of GE Dash-7 4-axle units.) These have lower engine hoods than mainline units, and have cabs that are significantly higher than the hoods.