"El Mariachi" is another indie that hasn't been digitally released in its original 4x3 aspect ratio (curiously the "Once Upon a Time in Mexico" supplements *do* show clips from the film this way... which is in turn a film that hasn't been on home media in anything *but* unmatted).
"Invasion of the Body Snatchers" was likely framed for standard 1.85:1 projection (which most films by this point were-- try this with "Plan 9 from Outer Space" and you won't see as many mistakes), which is what I'd love to see a digital release of the film in. I haven't checked too closely as to whether the ubiquitous 2.00:1 SuperScope blow-up crops this framing vertically or adds the 3mm to the left of the image that would have been covered by the soundtrack.
While I do believe many open-matte films were intended for widescreen framing, I do think almost all of Ralph Bakshi's work is better unmatted, Soderbergh's "The Good German" is a fullscreen-only DVD release I don't detest and Warren Beatty's "Dick Tracy" looks more at home in 4x3.
I have seen "Ben-Hur" in pan-and-scan on the 1988 MGM VHS (released on LD around the same time with presumably the same transfer) and I can see the OP's fascination, if this is to say seeing how well these films hold together in a form they're clearly not intended to be in.
By this point, the then-standard practice of letterboxing the chariot race was implemented with the frame zooming out as the horses entered the arena (I cannot remember if it zoomed back in after it was done or did a straight cut). The reel-change marks indicated this was clearly sourced from a 35mm anamorphic print, and it was no more than 2.35:1 (probably closer than 2.20:1). The American Widescreen Museum loves to gripe about the 2.76:1 negative ratio that all video editions nowadays use, stressing that the film was rarely exhibited in this aspect ratio and was widely seen in 2.50:1 (35mm, slightly letterboxed) or 2.20:1 (standard 70mm).
I will need to look through my Laserdisc collection to see what LDs I own in pan-and-scan/unmatted, mostly the ones I inherited as I'm letterbox-only on everything but VHS. It does include at least a couple 007 movies (The Spy Who Loved Me, Octopussy and the unofficial Never Say Never Again), 2001: A Space Odyssey and Ghostbusters ("Top Gun" is redundant since its 4x3 version was on the original DVD and the time-compressed "Star Wars" and "The Empire Strikes Back" because... well, you know).