Hi Norm, and thanks so much for replying so quickly.
I did mean 50hp because I overestimated the startup load on a soft serve machine. I don't need that much, but the LRA is pretty high for these things so I guess if I'm making something from scratch then I might as well get a small car engine. I've seen suggestions for engines from skid steers and so on, but that's going to be pricey, and other small engines are meant for high RPM and that's not suitable - I reckon a 1300cc Yaris donk or something like that. Smaller than that would be better, anything from a small car is going to be well and truly overspec for my needs but I do prefer that.
For the generator head, am I scrounging copper and winding my own poles, or should I be repurposing a large motor from something? Or am I barking mad and neither of these?