the same forms as if you got a 1099-B. in other words, in the investment section under sale of stocks. However, he has to convert his sales price and cost into US $$$$ for reporting. if he paid foreign INCOME taxes, he's entitled to a foreign tax credit.
It is more accurate to use the spot rate on the date of purchase to convert the basis and the spot rate on the date of sale to convert the sales proceeds. This is also the IRS's preferred method of doing conversions. The Internal Revenue Service has no official exchange rate.