A long time ago in a parallel universe I worked with 3D Studio R2 (ie dos software) and completed a number of projects with it. (I still own it, though not the 486 computer that ran it)
I can still open those files in rhino and other software, but there was another format you could save out of 3D Studio called .prj.
I can’t now exactly recall what that was used for; I think it saved animation data and maybe scene data.
Anyway, the trick was that in order to open these files in another program, you just renamed the file extension to .3ds, and the other program would be able to read the entities it supported.
I still have occasion to reference those original files, and up until V5 rhino could open those renamed files; however, starting with V6 rhino declined to open them, as does V7 and now V8.
If its not a major drama, could I request that the .3DS importer was tweaked to once again allow the opening of these renamed files?