Welcome to the forum! Save yourself a lot of headaches and build off a newer Savage or Stevens action. Leave the old 243 in it's current configuration and just enjoy it. As far as twist rate, you can order an after market barrel with whatever twist rate you want to suit your needs. Talk to Fred at Sharp Shooter Supply, Jim at Northland Shooting Supply or Devin at Sinarms, they all are forum sponsors and will help you all they can.
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