I wrote the permutation spec for Stable Diffusion necessary to merge with the git-re-basin method outlined here - https://github.com/samuela/git-re-basin. This is based on a 3rd-party pytorch implementation of that here - https://github.com/themrzmaster/git-re-basin-pytorch.
To merge, you may need to install pytorch 1.11.0 or lower (at some point, 1.12.0 did not work but the latest versions of pytorch may have resolved the issue).
Download the code folder, open cmd in the directory, transfer the desired models to the same folder and run "python SD_rebasin_merge.py --model_a nameofmodela.ckpt --model_b nameofmodelb.ckpt"
If not in the same directory then pathofmodela.ckpt and pathofmodelb.ckpt instead