long term capital gain / primary residence

My husband and I have both recently retired in 2018.   We are considering selling our home in 2019.  The long term gain (all qualified) will exceed the $500,000 exclusion.  If we keep our 2019 income below 78,750, the long term gain threshold for married couples, will our tax rate on the excess above $500K be taxed at the 0 rate?   I tried modeling this scenario using the 2017 home & business and received two answers one taxing the excess and the other not.