If the voltage is the same and you can make it fit it will likely work. I would replace that plywood also. What is the HP and GPM of the old unit versus the new unit?
Well it turns out that I didn't need to replace it. What I did was turn the shaft with a flathead screwdriver, and I could feel the corrosion. After several turns, it started turning smoothly. I hooked everything back up, bled the line with my hose (as required with the Voyager), and it seems to be working so far. Temp was 74 when I started, and it's now 77. I'll check again in the morning.