The 30-30 blown out that way is a .38-55 winchester, or 32 Winchester Special. the 38-55 doesn't usually have a shoulder at all but the 32 Win.Spl. does.
As far as necking a 35 Rem. down to 32 caliber you end up with a round that is virtually the same as a 32 Win. Spl. in a rimless configuration that would work easier in a clip fed bolt, pump or auto rifle.