Have a take off Kimber fluted target barrel chambered in 22.250. Diameter is 1 inch from in front of the threaded end to the muzzle and the total length is 26 inches.

I don't know what the thread pitch is for the barrel or for a Rem 700 action....so would this barrel need to be re-machined/re-chambered  and re-threaded in order to fit a Rem 700 action? I am guessing it would shorten the barrel by at least 1.5-2 inches to complete the work if needed, but I would have no problem with that.

Also would a .308 bolt head be required for the 22.250 round?

Rem Model 700: tenon threads are 1 1/16” x 16 TPI, with a tenon length of about 0.700”.  

Kimber barrels are pretty skinny - you may be short on luck with this barrel without a closer look at it.  You may consider adding a bushing to the barrel, but I don't know if this is practical in this instance.  Get an opinion from a good gunsmith here.  Either way, you are looking at a money pit for just a 22-250.  I imagine R700s in this caliber are plentiful under $500, and factory assembled at that.

If I saw a mix master rifle like this for sale, I would price it less than a stripped receiver.  I would NOT trust the skill of the smith with a high intensity round here.

Yes, a 308 bolt head is appropriate.

Thanks for the info and advice. Definitely some things to consider in order to weigh some options.