I’d love to see a restored 3-D copy of Robot Monster, which has only been released in 3-D on VHS (which never worked too well). Bonus: I believe it’s now public domain.
The other one I’d like to see is the only classic-era 3-D Warner Brothers cartoon, Lumber Jack-Rabbit from 1953, which has never been released on video in 3-D at all. Ironically, there’s a 16mm copy of it on eBay as I write this, but it’s the 1954 “flat” re-release.