CFZ -
I think you have this 24" machine confused with the mid 70s and later portables.
These portables did indeed use the same gearcase, motor, and pump, etc. along with a similar basket drive, and yes, they used a different belt, had a much faster spin speed, etc. They had a different, much springier suspension system than the larger machines for permanent installation.
But, the machine here is not one of those portables. It is essentially a full-size machine, in a little box. The baseplate is contoured a little differently, the tub and basket are a couple inches smaller in diameter (as well as one inch or so in height) but otherwise its the same machine. These use interchangeable basket drives, same belts, pulleys, etc. The spin speed is the same as the 29-inch machines.
Capacity is lower than the full-size washers, but not as small as the portables. I've been using a 1967 Kenmore 24-inch since the spring that Andy found in Reno. This was my first use of a 24-inch machine as a daily driver. It isn't the greatest in full loads of jeans as they seem to do better in a larger basket with more room to move, but the machine excels in loads of medium weight whites, sheets, etc. I have repeatedly enjoyed using this machine when I would have otherwise run a large capacity on 'medium' etc.
I think I said it above, but there sure doesn't seem to be many 24-inch Whirlpools out there.
Gordon