This very dramatic cover for 1969's Texas Rangers in Action #72 is Aparo's only Old West cover that I know of for the Derby publisher. He only contributes the cover art to this comic though. But that doesn't mean that's his only Old West action.
Aside from his brief but memorable run on Lee Falk's Phantom, the character Aparo spent the most time illustrating at Charlton was Wander, the naive but far from witless visitor from outer space, specifically the planet Sirius 5, who finds himself marooned in the Wild West of the classic American frontier. He gets as his guide and helper a Gabby Hayes wannabe named Jeb Dooley and P.T. Barnum type dubbed Phineas T. Bloat.
Wander debuted in Cheyenne Kid #66 and remained the sturdy back up in that strip for the next several years, with Aparo drawing many early episodes of the Sergius (Denny O'Neil) O'Shaughnessy-written saga before Fred Himes took over the reins of both script and art eventually when Aparo and O'Neil headed for the bright lights of DC Comics and eventually the shadowy alleys of Gotham City a year or so later.
Here is a very Groovy link to Wander's debut.
And here's another to his second appearance in Cheyenne Kid #67 which wraps up his "origin". This was my first sample of the Wander adventures and one of my very first experiences with the muscular and compelling artwork of Jim Aparo.
Wander drawn by Aparo would appear in these issues of Cheyenne Kid.