Judging by some of the prices, it would seem to me that you're better off buying a complete rifle with the action you're looking for and replacing the barrel and stock. This way you would have a second barrel for it.
To clarify what I mean. If you're looking to make an 338-06, just buy a 30-06 savage and replace the barrel.
The actions I saw were almost 400 bucks. I bought my savage with a scope on it as well from dicks for 431 dollars after taxes. And it's a real shooter. And I can always get another barrel(s) for it too without needing to buy a stock as well.
Course my gun was on sale, but everything goes on sale sooner or later. A little patience might get you what you're looking for and then some in the end.