The prognosis is pretty grim. The Big Gundown is available unofficially as the Franco Cleef version in R1. Death Rides a horse has some crappy fullscreen public domain cheapy releases. Face to face doesn’t have a R1 release yet.
If you don’t have one already, its an absolute must for a spaghetti western fan to have a region free player. I would suggest getting a region free player or downloading VLC player to your computer and watching the Pal 2 MGM release of Death Rides a horse.
Also Koch has a boxed set of all the Solliima westerns. Unfortunately they are only in foreign language with english subs.
ANother option is to get the japanese ntsc 2 release of face to face, but its very pricey.