...and then there was the Captain America of the 1950s book published by Atlas Comics (a precursor to Marvel Comics), at a time when monsters ruled the comics!
"The Real Captain America"
In comes William Burnside, a devoted Captain America fan, had surgery to look like Steve Rogers (and even legally adopted his name). Burnside recruited Jack Monroe to be his Bucky, and the treated the two to a version of the super-soldier serum...and they fought the red menace of Communism...at least until the two went crazy and were locked away by the U.S. government for a time.
Captain America Returns
Burnside then returned again proclaiming himself the real Captain America in Captain America #36-49, #600-605 (2008-2010), when the original Bucky served as Captain America for a time.
This Nomad even ended up with a four issue mini-series and a twenty five run in his own title for a time in the 1990s...
Captain America History
Captain America Comics #76 (May, 1954), Young Men #28 (June, 1954), Men's Adventures #28 (July, 1954), Captain America Comics #77 (July, 1954), ending his reign of terror in Captain America Comics #78 (September,1954).
All this covers Captain America until he's found by the Avengers in Avengers #4 (March, 1964).