Jim920, do NOT fire a .358 Hoosier round in a rifle chambered for the .358 Winchester. There would be way too much headspace. And, there exists the possibility of a ruptured cartridge and/or damage to the rifle and/or the shooter from gas leakage.

The Marlin X7 short action in 243 is a good choice to rebarrel to .358 Hoosier. The first rifle chambered for the Hoosier wildcat is my Marlin XS7 that originally sported a .308 Winchester barrel. Of course, the rifle had a new barrel chambered and installed by a gunsmith. It is possible to have an existing barrel that is currently chambered for the .358 Winchester shortened and rechambered for the .358 Hoosier. However, you may just as well start off with a barrel chambered for the .358 Hoosier. You would probably be money ahead, possibly avoid a lot of frustration, and possibly not be satisfied with the fit of the modified Shaw barrel in your existing stock.

Please check with one or more of the sources of .358 Hoosier “stuff” (reamers, rifles, barrels, ammo, etc.) listed in an earlier post (dated April 03, 2013). Some of those sources could better answer your last question than I. Good luck with your project.