Is it the MSC-SL (super light)? I saw a photo of it and I don't think you will have any issues especially with a number 4 contour barrel. I am not to sure on fitting a 50 mm (with regards to ring hieght) objective but the 40-42mm objectives should work fine, especially if you use the proper scope ring heights. Lastly, it's your custom rifle
so if the stock is comfortable and you like it then you should keep it. Comfort is a major factor in successful shooting.