I prefer a 10-16hp engine myself on a workhorse that'll push/blow snow. Thinking about it, I am of that opinion only because I've never had an opportunity to use a lesser engined tractor equipped with a plow or blower. I really don't see why a 6-8hp tractor with loaded tires and chains wouldn't be able to do the job as long as it can run the PTO at the required rpm (for a blower) and still move the machine (for the plow). I think you could do a good build with an old frame and your motor as long as your expectations are realistic.