"Can" you? Well of course you can, you "can" report anything you want.
But "should" you? Really, no, not if the broker is reporting the cost basis to the IRS. The broker at some point asked you how you wanted to determine basis for the sale of stock, and told you FIFO would be the default method if you didn't respond with another default method to use. IF you want to actually select lots of stock to report as the basis associated with the sale THEN you need to tell the broker what lots to sell before the trade settles.
As a practical matter basis reported by brokers gets changed all the time, due to quite legitimate reasons, so I'd guess the chances of being audited would be very slim.
Tom Young
