Agree - 3/4 hp would likely be plenty. Since you won't be pushing it to beat the clock (I assume), if you start to overload the motor you can always back off a bit.
If 'twere me I would probably try to find a used 1hp 3 phase C-face (I think) motor and get a VFD to do the phase conversion and get variable speed. Used 3 phase motors are often pretty cheap.
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