Regarding the.35 S&W cases made from .25-20 brass, Donnelley's "Manual of Cartridge Conversions" recommends using .32-20 cases for a starting point. Of course, below the shoulder, the .25-20 and .32-20 cases are dimensionally identical. But I'd think .32-20 brass would be easier to come by. Most who reload the .25-20 simply neck down .32-20 cases.

But it is surprising that anyone would want to undertake the considerable labor of making .35 S&W brass from .32-20 cases, when .32 ACP cases work just fine in the .35 pistol. Especially so when the likelihood of finding .35 S&W reloading dies (other than by having a set custom-made) is essentially zero.

By the way, Donnelley's manual is a valuable reference for almost anyone, even those who have no desire to custom-make odd cartridges. It is an absolute treasure trove of data on just about any cartridge ever made anywhere at any time, including metrics. It is one of my most-used reference books.