Kirby’s contributions to the interiors in the Marvel westerns dropped off in early 1963, after all the super-hero books were launched, with just a few short bits after that. He stayed as the artist as most of the covers until mid-1965, though. This is the last issue of KID COLT OUTLAW to have a new Kirby cover, and he went out with a bang, pitting KC against over a dozen fully rendered bad guys.
No agreement on the inker of this one. Dick Ayers is sometimes credited, but that doesn’t seem to fit. The GCD entry has apparently had Ayers, Jim Mooney and Carl Hubbell at various times. Don’t think I know of any credited examples of the latter two inking Kirby to compare, and 1965 seems a bit early for Mooney to be inking at Marvel, since he was artist on Supergirl for a while.