Correct, it is important to reconstruct the individual stock line item and edit the cost basis and its description. Essentially you need to go through old broker's statements, if you can. If you can't figure it out, then you really would need to use a basis of $0. The proceeds would then be taxed as a long term capital gain. But if the proceed and the cost are the same, it would zero out, as you mentioned.
@shazyalex
