I took at look at my ACME belt sander. It's a 3/4 hp 1725 rpm motor. It's a direct drive, not pulleys. Just a 6 in(?) dia. rubber wheel on the motor. It take a heavy and long cut to stall it out. This is not mine, but it looks just like it except blue and dusty.

I still think a 1/2 hp would OK on yours. You might stall it occasionally but sharp sandpaper makes a big difference.

There are a few of us that like to restore and use old machines and I am one. I am not familiar with that sander but generally the older stuff, even the cheap ones are better than most new stuff unless you get into the higher end products. Sure you can go buy one at the BORG but assuming no hidden problems you will probably have a much better unit there once you get it done. Have to watch it, it is as addicting as building boats.