Can't see if it has the slow speed on the benchtop model. It would be most evident in the one where it is pointed towards camera left, but could easily still be hidden by the angle. JZiggy has fabbed up some, but they cost about what you would be into both ($115 IIRC?). Again, easiest way is to ask if it has two or three pulleys. Depending on what you are doing (and how much you want back), you could always mount two tables on the one you keep, or remove the table part of the bad one to have a collar so the good table can't slide down past a certain point. Helps when you loosen it not to have it want to drop. The motor on the bench one is the one I would keep, as it is a match for the timeframe of the drill. These were sold with and without motors, but I have a strong suspicion that if ordered with a motor, these were what were supplied, as they match HP and RPM, and were in the same catalog (so easier to take a "general purpose motor" and sell it as a package, rather than have a specific one for each kind of tool).
The size of each pole should be a direct match with regards to the diameter. The best option would be if they were direct matches with regards to the manual. 103.24500 and 103.24510 for example. I know some of the 150's have a sheet metal return spring, and others have it inside the head. Looking at the side opposite the handle will have either one or two chrome knob thingys. The front one is the quill lock, and the (possibly?) second one is the return spring. If it isnt on the outside, you should be able to peer inside and see it behind the steel shaft (quill) towards the front of the head, attached to a roller pin inside. Not a big deal if they aren't a direct match (with regards to the quill return), as nobody will know any different. You just need to make a note of the model number for manual reasons (if they don't match).
This applies to the one with an internal spring. Even if the return seems a bit sluggish, they are easy to fix or replace, and Sears even carries the spring. Sometimes they just need a bit more tension, and others need a new spring (>$20).
This applies to the one with an external spring. These are a bit trickier as they have steel banding wound into a spiral. They are also easier to break when doing a complete teardown if not working. I would be more cautious if it was this model and the return was not very strong trying to repair it.
My plan was to buy it, then when a floor model came along, swap out the head (or just the pulley system) and sell off the bench model.