No standard answers for these questions, only choices and opinions.
Without knowing cartridge details, or having a book in front of me:
New barrel, cost varies depending upon what you want.
Bolt head - About $20
Stock - Depends on what you want. $300 McMillen, or a $100 Boyds.
"Most accurate" doesn't exist. If you think Dunlop tires are better than Bridgstone, great! But there is no universal answer.
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