It's starting to come back to me. You had to pay extra for a "High output heater."
That makes sense. My father ordered a '78 F150, which in itself was a step above the F100. He wasn't one to pay for frills but wanted carpet as he was tired of water getting trapped under the rubber mat and not escaping. Other options he was looking for were limited slip and rear sliding window, and he bought the 302 4-speed.
I never felt that the 302 was much of an engine. I had a couple of 300 I-6 pickups which had as much if not more power. Either engine could give around 18 mpg though, with the 4 speed creeper transmission. They also seemed to be pretty tough; it was easy to get 100K + at a time when many engines were toast before then.