[crashryan]

My guess is that it was a contractual thing, like the Panther says. Massey's contract probably specified that his likeness couldn't be used. The artists drew the replacement Dr Gillespie the same way in all the issues, which suggests his appearance was a conscious choice rather than an artist's quirk. It took them a couple of issues to get Kildare's hair the right color, though. Maybe they didn't have any color reference photos of Richard Chamberlain. Speaking of the art, I don't see any Robert Jenney here, and the inking is definitely not McCann. My best guest for the penciller is Norman Nodel, who did a fair amount of work for Dell around this time. The inker is a puzzle--it looks an awful lot like Ed Robbins, who also worked for Dell. But I've never seen Robbins ink anyone but himself. With issue #3 the art went to Vince Colletta's studio.

Link to the book: Dr. Kildare 2