The 2004 SEs were not scanned in 2k, they were scanned in 1080, so the master negative is the same resolution as the HD version. I have no idea how the 4x3's were derived. It's possible that they just cropped the SD downconversion, which is what many 4x3 transfers are. Given that there was never a 4x3 HD release/broadcast as far as I know, I'm going to say that it's less likely that a 4X3 HD crop was made that was then downconverted. The 4x3 version was designed only for SD broadcast and DVD, so I wouldn't be surprise if they went the easier route of just cropping the WS downconversion.

The 16x9 HD crop shouldn't net you any higher detail though, since the negative master is itself HD--it's just a blow-up.

So perhaps none of the fullscreen releases are any better. There might be hope though, since the broadcasts are so compressed that the blow-up would reveal detail that got lost in the compression. The compression is applied during broadcast and isn't on the master they recieve, so in this respect even though the fullscreen is a blow-up you might get information thats not on the widescreen version.