I’m having the same issue with my Texas taildragger conversion. The leaf spring needs re-arching and I fear cold bending would damage the springs or crack them. Not to mention the FAA interpretation of allowing this type of repair.
The leaf springs parts are not available so I’m looking at having a set of springs made.
Problem being obtaining FAA approval and obtaining the data / specs. Drawings only give the STC part number and according to the STC holder they have proprietary rights to the data. The STC holder gave little encouragement that future leaf springs would be made. So the dilemma. Need to restore but parts available. Would like to have made but no data and I need FAA approval. I would hope a owner supervised manufactured spring according to the current part would be allowed, but only approved for my specific aircraft. Any and all suggestions will be greatly appreciated.