There are several threads on pto powered lawn vacuums. If your eliminating the gasoline engine why are you buying an expensive frame that has to be remodeled ? If you have the capabilities of welding and cutting buy the housing / impeller from a walk behind unit. They are available for fifty to seventy five dollars, sometimes even free on CL. Some bearings, shafts, pulleys and a section of eight inch hose... and don't forget belts. I built one for $150.00 and it works great. The scavenger hunt for parts is the most fun besides testing the actual product. Take a look under build it yourself forum and get some ideas. Before you know the creative mind has it built before the first piece of metal is cut. A real fun satisfying project. Good luck and looking forward to your version with of course pictures.
PS... We need a picture of the puppy. My assistant is a soft coat wheaten terrier.