I suppose you could if you absolutely had to, but there is enough difference between the two cases that it would not be entirely satisfactory. The 350 Legend head size is .390", 351 WSL is .377", so the brass would need to be base-stripped. The rim of the 350 Legend is rebated, measuring .378", 351 WSL rim size is .407", so extraction would be an issue. Most people make 351 WSL out of 357 Maximum brass, the only thing you have to do is turn the rim down about .020" and trim to length.
