Captain America, vol 5 (start date 2004), issue #34 (published 2008).
Art by Steve Epting
First appearance of Bucky!Cap.
Bucky Barnes, day 17
Bucky’s initial, reluctant motivation for being Cap relied heavily on him not trusting anyone else to do it. He pushed through his discomfort and fumbled his way into the role, in an attempt to honor Steve’s legacy.