I did replace mine with a 1/2HP 3-Ph motor using a VFD with no problem. It will still stall in top (drive belt) gear if I do something daft or a large drill plugs up. It's never been an issue though …. more of a convenient safety factor than anything else. I don't feel any real need for higher power than that.
As I recall years back when I asked around, the consensus was that, with the 1/3 HP motor, the machine was a bit under powered and that 1/2 HP was better. There were doubts about going much more than that – but whether based on practical experience I couldn't say.
3/4 HP is more than twice the original design power.
Edited By Bandersnatch on 08/07/2015 17:25:26