Henry doesn’t seem to be in any hurry to make their single shot in .360 Buckhammer as they originally advertised, so I was thinking of having a single shot rebored. But I would be looking for something cheap, since it would cost about $300 for reboring.
Maybe something with a rusty bore. A nef rifle or an Encore barrel maybe. Or a Ruger possibly, for the right price

Try Johnsons gun shop in Adrian Mich. They may be able to help with your project

A 357 Magnum single shot rifle would only need to be rechambered and modification of the extractor/ejector. That would cost about half as much as a rebore. As good as JES is at reboring, he struggles with extractor/ejector modifications.

What’s the normal twist in a .357?

Help in what way?

Anywhere between 1:14" and 1:20"