How much time is spent each winter below freezing?
It doesn't get that cold here. The furnace is safe in the attic. The only problem I've ever had with 90% furnaces was about 4 years ago when the drains that ran outside freezing and causing condensate to back up, and nobody I talked to could even remember that happening aside from that one winter in the last 15-20 years. Put heat tape on them and be done with it. The only thing I would be worried about is putting a Kenmore in. I don't know anybody who sells parts locally for it, aside from obviously Sears. I had to get a defrost board for a heat pump this last year and it took about a week to get parts.