I wonder if it really matters what the original cost basis was.
your donation is the lower of the original cost or the current market value. the 'sticks and stones' of a home depreciate over time (it's just the land value that causes the home to appreciate). So unless there was significant gold inlay or some sort of appreciating material (highly unlikely) in these cabinets, they are worth less now than when you purchased the house.
here are the instructions for the part you are questioning:
Columns (d)–(f). If you have reasonable cause for not
providing the information in column (d), (e), or (f), attach
an explanation so your deduction will not automatically be
disallowed.
You know D: 2012
You know E: "part of home purchase"
for F: personally, I'd include a statement that is it presumed the cabinets were worth more in 2012 and have depreciated since.
just my two cents
