Yup, here we go again. LJ won't let me post longfic here in one piece, so LJ gets links to DW and AO3.
we don't need a heart of gold, we need the heart of a lion, 17k(!) of Avengers AU fic, Steve/Tony, NC-17, 'You know what's an interesting plot bunny? And I'm sorry in advance. If Captain America was an alternate personality of Steve's or vice versa.'
AO3 link!