Are you wanting to do this yourself?
If so this process involves some specilized equipment the biggest is a barrel vice
and a action wrench. Which can be had from Brownells
Then you are going to need a 264 win mag barrel. There are many different manufactures out there. I like Kreiger and Bartlin for barrels. they both single point cut rifling which induces no stress on to the barrel. Bartlin was started by a few guys who left Kreiger too. Once you settle on your barrel it may or may not be chambered It is better to get it un-chambered and have it down with the action at the smith. This is not something you can do you self unfortunately. You're also going to need go no go gauges and plenty of other stuff like a lathe ect....... You can get prechambered pre cut barrels for a 700 but what is the point in that. that is like spending $2k to be a factory barrel back on.
You action will also need some work as well. This all adds time and money.
What I would do is this. Contact
3464 Messersmith Road
York, PA 17404
Phone: (717) 792-1069
Bob Green Home
I have seen and shot his work and it is very good and at a decent price. I was out shooting with a buddy of mine who juts had a Ruger 77/22 hornet rebarreled into a 17 AI Hornet. We were fire forming loads for it and still getting amazing groups at 100 yards. best of the day was a 5 shot .3" group I shot.
A barrel swap is not simple. there is a lot of machine work involved to do it right and look for this to cost you when your done. $1000 to $2500 depending on what you have done. Plus if you get a contour that doesn't match the stock contour of your factory barrel your going to have to either order a new stock or have the stock one reworked to fit a new barrel contour.
Hope this helps a little bit.