The classic covers are the one's that I enjoy the most, unfortunately they are not available on any of the comic books.
The notable exceptions being Bama inspired covers on Gold Key and Marvel's Doc Savage magazine from the 70's. Steranko and Kane did some excellent covers on the Marvel series and Kubert did some classics for the DC comics. Stelfreeze did extremely stylized Art Deco stuff on the Millennium runs, and there were some incredible covers that hearkened back to the original pulps of the 1940's on the . In terms of composition and style I have to say that I am waxing nostalgic with this one...
Happy 75th Doc!