I have the exact same problem as Bigley. I get the correct aspect ratio when I use my hardware on VLC media player. VLC is tough to use, however, since it only saves files in .AVI format and for one VHS tape that equals about 350 gig of hard drive space. I suppose I could convert the giant file to MP4 with other software, but I'd rather avoid that inconvenience by using OBS.
When I look under View>>Multi View (Fullscreen) there is only one option for an aspect ratio., ie. (1):1280x1024@0,0. Changing the resolution doesn't change this but only crops the VHS image into that size box. Since I am not going to upload these VHS files to any website, I don't want to crop the image. Since the lone full screen ratio is labeled "(1)" I am wondering if their once was a choice in earlier versions of OBS that have since been removed from the list, ie. (2), (3), (4), etc . Since all earlier versions of OBS are still available on the download web page, I was wondering if anyone remembers the earlier version that may have contained the 4:3 aspect ratio so I can use that version?