The old site search from Google needs to be updated. Use the Search at the Upper Right, or use What's New in the center - it has a drop down arrow. You will need to change your Favorits by right click mouse and clicking favorites. Many of the posts in How to Use This Web Site are old so the links may or may not work. I have one hell of a lot of work to do!
Down through the years, I owned a couple of SB 9 lathes and both had 1/2 hp motors on them. I replaced one with a 3/4 hp because I had one and the original needed bushings. I may still have the original motor.
I sometimes wish I had the second one back--it was a 9C with 2 chucks, faceplate, taper attachment and was in really good shape.
I purchased it from the original owner, a basket manufacturing plant, where it had been bought new in 1947. I even had the original shipping invoice and order from South Bend. I was sure that I needed "bigger" and newer, but it was a good light machine.
On flat-belt drives a general rule of thumb is 1HP/Inch-width of belt.
The two SB9s I have both have 3/4" belts. I'll have to check the specs, one might even be on the original motor.
The other is on a 3phase 1.5HP, way more than it needs but it was the closest motor to hand when the old one died, so that's what went on!