I need help!

My husband has an old Delta Milwaukee bench lathe from the 1940s. The problem is that the motor is too fast for the turning he typically does. On the lowest setting, it's still faster than the highest one on his previous lather (3200). I would like to surprise him with a new variable speed motor for this lathe, but I'm way out of my element and don't even know where to start.

Any help would be great appreciated!