Going into TAB menu/Video Options and changing from "Pacman Upright Artwork" to "Standard (3:4)" looks identical to the posted screenshot, except without the artwork.
Selecting "Pixel Aspect (7:9)" looks like it gives evenly sized pixels, but isn't that option what you don't want to do? e.g. isn't that "fat Chun Li" mode?
H@P
EDIT: Sure enough, set mslugx to "Pixel Aspect (10:7)" and lose the "shimmering" scrolling. Add a little -waitvsync to lose tearing. Butter.