I've done that, moved mine back 1.5 inches.
1. Cut through frame engine support horns near their ends and added tubing spacers to extend horns.
2 Extend front tranny mount by cutting it off and adding spacer between it and the torsion, with extra bracing.
I did all this with tranny in place to make sure everything was all lined up, tack welded the new mounts, so I could still move things around.
3. Removed tranny, then welded all the extended mounts up.
4. Mine is mounted top and bottom of the bellhousing.
I supported tranny with ratchet straps from the frame, while I was extending all the mounts.
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