You did not state if you prefer a wood or composite stock. Go to Stockade Gunstocks and take a look at what's offered. The Long-Range Benchrest model with the various options offered might be your ticket. Call Kevin and he will work with you. But be prepared to wait several months for a custom benchrest stock. Richards Microfit offers several custom wood benchrest style stocks with flat, wide forearms. But you will need to do some final fitting, sanding and finish work. Also a pretty long wait.

I have a Savage SA with light varmint Accutrigger, 6mmBR 10 twist 26" McGowen varmint barrel and Richards Marksman stock that shoots 65 gr V-MAX's with impressive accuracy out to the ranges you mentioned. I expect it would shoot a 87 grain V-MAX or Berger bullet with similar results. If I needed a new 6mmBR barrel, then it would most likely be a CBI barrel from Northland Shooters Supply. I've purchase one in .204 Ruger and 6.5x284 with light varmint contours from Jim at NSS since I got the 6mmBR McGowen. The CBI is a great custom barrel for the money. Not much to dislike about my 6mmBR. Easy to find an accurate load for and less recoil with plenty of reach for long range Pdogs makes for a great day afield.