Precision Rifle does a complete conversion on a Remington 308 or 243 for about $500. He uses a Green Mountain barrel and i don't think you can select the twist. I think his are 1-28.
http://www.prbullet.com/700.htmI like the 700ML with a McGowen or Pacnor barrel better. The McGowen saves you about $100-150 and its still a great barrel.
http://www.smokelessmz.com/pricelist.htm