Interesting, am also in early stages of building one.
I plan on using a walk behind snowblower as the traction as it provides varied speeds and build up the front framework with a wide full swiveling wheel or maybe even 2 full swivel.
It will be side dumping.
I have feelers out for a discarded blower frame and one friend said to take the one he was about to haul off to the scrapper.
Problem is that it took me all of 1/2 hour to do a complete tune up/ repair and I now own a 13HP 33" MTD c/w electric start that looks like new and starts 1st pull.
Ideally what I wanted was an old Ariens, 24" w/o motor as I have a few in my project pile.
For power anything in 3-5 hp is all that I'd need and that I have.
Another neat candidate was a discarded electric golf cart that I am still contemplating.
Also have access to a discarded electric wheelchair that could become a suitable doner .(if I decide to go electric)
