depends on the pump
Ive seen one built off a 1460 combine pump it can be done but may be a lot of hassle's,,,,,and was slow ............ is it belt driven what rotation it is how many gpm is it rated........pump may have a tapered shaft........ i also had this idea i have a old 1460 parts combine that has the pump and tank but the pump is ccw so you would have turn the pump over to get it to turn in the direction of the motor your doner may be different,,,,,,,, gpm is really need to know determans how much hp is required
getting the speed right on the belt so that cycle time is not way to slow or to fast and kills the motor could be hard even if you know the pump size
I'm all for making stuff with extra parts but you will be money ahead getting a 2 stage pump even if its only a 16 gpm and ive seen them for $120, singel stage pumps require more hp as i have been working on building a 20 hp splitter with a singel stage with out spending a lot of money