Thanks qbteachmt!

Our tax valuations for property is typically well below market here in MN as well. The example I referred to said to get the ratio of the land to house as you indicated.

They do meet the citation you posted:

(3) Vacant land—(i) In general. The sale or exchange of vacant land is not a sale or exchange of the taxpayer's principal residence unless—

(A) The vacant land is adjacent to land containing the dwelling unit of the taxpayer's principal residence;

(B) The taxpayer owned and used the vacant land as part of the taxpayer's principal residence;

(C) The taxpayer sells or exchanges the dwelling unit in a sale or exchange that meets the requirements of section 121 within 2 years before or 2 years after the date of the sale or exchange of the vacant land; and...

And thanks for the link for research help!