For the barrel and the tools needed (barrel nut wrench, receiver wrench) start here Northland Shooters Supply
There is a target action for sale right here on this forum for an unbeatable price right now if you don't wait too long http://www.longrangehunting.com/foru...educed-113359/
If you scroll down a few posts you will see it is listed at $475 including shipping to your FFL. (post 7)
Jim at NSS has some barrels on order at Shilen which at this point do not have chambers specified, so I would not delay too long before speaking to him. On that subject, CALL the guy during office hours. Basically forget about email, the guy operates old school.
The action + a Shilen barrel will be an excellent start for a very good gun. You can look at stockys stocks for a stock. You want one for a blind mag since the target action is not set up for magazines. Like this Bobby Hart Long Range Target / Tactical (LRT) Remington 700 BDL / Savage 10/12 (4.40) Laminated Heavy Barrel Riflestocks (Right & Left Hand Models)
If you must have a rifle with a magazine, speak to Jim at NSS because he has the varmint actions on order from Savage, so far I don't think he knows when he is going to get them. That way you would get an action with bottom metal and magazine with the right bolt head all ready to go. Starting off a model 12 is another way, and thats what I did, but I only paid $770 for mine, not $900+. I do see that the 12LRP has a fiberglass stock, but for sure a barrel that is unsuitable for what you want to do. It is pretty hard to get money back for factory barrels...