The ejector conversion is easy with a .30-06 family ejector used in place of the 357 ejector, an extractor barrel would be even easier since the extractor follows the rim, conversion instructions for a rimmed to rimless ejector can be found in the FAQs, MSP and I have done the 357 to 35 Rem conversion on our ejector barrels.
I've shot 240gr cast bullets in mine with no problems, the twist issue may be an problem for 250gr spitzers, but I doubt seriously they'd work well at 35 Rem velocities, round nose 250gr have been shot in the 357max just fine.
Tim