A new take-off barrel in a Rem mountain rifle contour might be a little hard to come by. Not the typical donor rifle that someone would purchase for a project. Lots of custom barrel makers can make one to the exact contour you specify.
Custom barrels can be a little pricey, but they are well worth it. Sniper's Hide has a section on "group buys" where you can sometimes get in on a group order with a 10-20% discount of current prices. I have a Brux on order right now for my Rem model 7: a 2.5 "special designed" contour in chrome-moly which will be fluted. At 22" it should be fairly light weight. Something along those lines might be of interest to you.
I have a 270 mountain rifle takeoff barrel I would sell for $50 plus shipping. I bought it used but I don't believe there were many rounds through it. It does have a couple of small scuffs where it was removed and a small rub on the side of the muzzle. Pm me your email if you are interested and I'll send you some pics.