I wouldn't play the egotist by waving an 8275 red flag to tell the world "I'm special."  This is no different from calling a mobile home a primary residence, for purposes of claiming the mortgage interested deduction.  In fact, you don't tell us that it's not a mobile home.  Or a houseboat, for that matter.  

But @sjrcpa 's question points to the right answer.  You have two transactions.  A sale of the structure, and a sale of the lot underneath it.  Exclusion applies to the former but not the latter.