Generally they are called "Motor Wheels" as that's the company that made them, similar to "Budd" wheels but different.
The distinguishing feature is they are hub piloted, the bore in the wheel snugly fits and is located off of a spigot on the hub.
At he time Chevy and GMC mostly used their own hub piloted 10 lug wheels on the larger trucks, these could have been made by a few different manufacturers. Best I can tell the 5 lug "Motor wheels" as the name implies were made by Motor Wheel.
I've most commonly, although somewhat uncommon, seen these 5 lug motor wheels on GMC trucks in the 50's.
Edit-- and apparently earlier
The 10 lug on 7.25" circle is much more common on the GMC, and as far as I know the only choice on AD Chevy trucks.
More wheel info here, but not specifically about "Motor Wheels"
http://www.stovebolt.com/techtips/wheels/Grigg
