As far as custom Rem 700's are concerned, G&A Precision (George Gardner) tops them all. I have shot the T.B.A. and I.B.A. rifles, and they are precision weapons indeed. (note: the I.B.A. one piece scope mount/rings is one of the trickest parts I have seen for this rifle) IMHO, and in my experience, George makes the most accurate rifle I have ever witnessed. My shooting partner has one of George's rifles, and the accuracy could best be described as "monotonous". We have only shot it @ distances up to 500 yrds, but the largest groups have been .5 moa. Other items of interest might be his turn around time (three weeks on customer supplied Rem 700 PSS for my partner), he uses the 5R barrels, and he is a shooter. Last time I checked, his prices were VERY competitive. If your looking for this type of rifle, you owe it to yourself to check out G&A Precision in Kansas City, Mo.
Note - The only benefit to using the "old" Remington bolt sleeves that I am aware of, is that they are necessary to install the "speedlock" firing pin.