Interesting stand, appears to be made from pressed steel and welded, whereas the old Singers were cast and bolted together. My 51W59 stand was pressed (heavy) steel but was still bolted together, not welded. I had a similar pulley stack/clutch on one of my machines but I ditched it for a servo motor. The original motor, in my case a Singer, was very old and so was all the wiring and I considered it a safety hazard!
I doubt if the motor's original or that it came with a step pulley, my Singer motor didn't, you just adjusted the motor position if changing speeds.
The timber top looks solid and it might be worth sanding/cleaning it.