In 74/75, IH moved the engines back in the pickup/Travelalls. To
accomodate this, they changed to the rear-sump SII setup (69-73 (and
earlier) the oil pan was in front of the axle, in '74 it's half behind
the axle).
They didn't use a double-hump pan, though.
The truck pan sits as low in the front as a SII pan, and about as low in
the back as a SII pan, but the front depth continues back to the rear
sump, instead of "humping" like a SII pan.