Have Redneck cut barrel at 24", chamber in 7mm Rem, throat it for 180 scenars. Bed it yourself. $425 $340 $400 Plus Redneck's costs. I like a 7mm way better due to the better bullet choices but if you really want a 257, just find a barrel in stock and rock on.
The better solution is just to buy a Kimber Montana in 7mm-08 and put a good scope on it. Way less money and the way I'd go if shooting righty.