I'm sure back then an acre of property was a few hundred dollars compared to today.
Be aware that I am by no means a legal expert. As I see it, your cost basis is the FMV on the date of his passing. As support on that assessment/assumption, I see the fact that you paid property taxes on it (and can prove it) for the last 20 plus years, thereby "treating it" as if you had already inherited it.
I'm fairly certain that to that cost basis you can add any and all costs incurred in the process of getting your name on the deed. So that would include all legal costs along with whatever you paid to the cousins and other relatives.
As to weather you would be required to issue some type of tax reporting document to the cousins you paid as "proof" of your cost basis valuation, you might want to check on that, as I really can't be sure. Either a real estate attorney (not an agent) or maybe a tax attorney (not a CPA or EA) should be able to clarify that.
All my above comments are not based on any facts that I can cite or prove.
