I have a 30+ year old Sears Shaper 113.239201 and the 1/2hp motor is on its last lap. It is a 1/2" spindle and has worked alright. Bushing let it accept 3/4" cutting bits, but its a little underpowered.

Issues of motor mount compatibility aside, how large a motor would stay withing a safe operating range for this machine?

I am not thinking of anything crazy and feed speed is not that important to me. I would like cleaner cuts in harder woods. So, would a 1hp or 1.5hp motor with the same rpm stress the bearings or the spindle? Heck, I have a 5hp 220v motor gathering dust, it weighs more than the shaper and seems a bad idea. But what do I know.