u/Hysteri-cal

Family property (vacant land in NC) was signed over to me and my spouse in the late 90’s. My parents inherited some of it in the 80’s and purchased some of it in the early 70’s. When this land sells now, the capital gains will be huge. I am not even sure how to go about calculating the basis. For the inherited portion, would it be the stepped-up basis from the date my parents received it? No records exist for the sale in the 70’s. Should I try to find comparable sales from these time periods?
Thanks for any ideas to calculate the basis and minimize these gains. A 1031 exchange doesn’t work for us right now unfortunately.