1,900 sq ft split level CBS ranch, circa 1964, with a flaky natural gas
furnace, in the temperate Portland (OR) Metro Area.

Time to replace it. Currently, have a Lennox Conservator III G16,
Model: G1603/4-100-3, Input: 100,000 BTU/Hr, Air rise: 35-65 F, and
ducting to match. Only have 5,000 sq ft of lot, and drilling is not
practical, so practicality of a ground source heat pump doesn't seem to
be there.

If you have recently replaced your furnace, would appreciate hearing
how you did it and what you learned.

Thank you kindly in advance for your on-topic remarks. Sales droids
will be spaced, out the airlock, ga-WOOSH!