Update: The manufacturing methods used to make these cameras means that my design might not fit your camera, so I've added the STEP files that you can use as a starting point to tweak it until it fits.
This is a 100% printable replacement back for a 3x4 Graflex SLR that enables you to use 4x5 sheetfilm, rollfilm holders, or a Lomograflok with your camera.
You'll need 4 M3x4 heat-set inserts for the locks / springs to hold things in place.
This fixes the orientation into portrait.
Remove all 12 screws holding the 3x4 back into place. Remove and replace it with the 4x5 back, and replace all the screws to keep it firmly in place. I haven't noticed any light leaks, but feel free to use light-proofing foam or felt between the camera body and back if you have issues.
For sheetfilm and roll-film backs
For Lomograflok
The author marked this model as their own original creation.