Indeed, these "big" trucks are kinda small compared to today's full-size pickups, the operators have gotten bigger as well. The big 1948 Pilot-House brochure has this comparison of small 130-lb and large 220-lb driver, showcasing the new larger cab. Judging from the locations of these two drivers' eyes, shoulders, and knees, the big guy is about 6 ft tall-ish, small guy maybe 5'6"...Andy Taylor and Barney Fife sizes.
This reminds me of the time some big ol' boy moseyed up to the house wanting to sit in one of the Pilot-House cabs on the side yard. He wanted to get an old truck to fix up, but made the smart and probably experienced decision to see how he fit in this "great old truck" as he kept rambling on about. So I opened the door to the one that I had driven last, he climbed in, and the look on his face said it all as the steering wheel scraped his belt buckle...he decided that these old great trucks were nice to look at, but not quite his size