Yup, I noticed the 1962 footage in "Moon Trip."
Though they only used molds to make the characters from the 1960s onward. In the 1950s shorts, they were made with rolling pins, cookie cutters and stuff like that, making for a more interesting style. Any new footage did use something resembling the 1960s Gumby mold, but with his 1950s-style red-pupil eyes and rubberband-like mouth. IIRC, Gumby did not speak in the new footage made for 1956 episodes, but in the 1957 episodes he did, since Dallas McKennon voiced him in those. With this new footage, Art Clokey would also voice Pokey, which explains why he spoke while Gumby didn't at the start of the re-edited "The Blockheads" (that honky-tonk piano theme was kind of out of place with that scene of them running into the book.)