Winchester Model 74 Barrel Replacement

I have a Winchester Model 74 that needs a new barrel.

I have the replacement barrel, but so far the 3 gunsmiths I've tried have said they were unable to work on it. I even tried a gunsmith that was listed on the Winchester gun site. (Dorn's of Macon).

This was a great granddad's gun and fed the family. Would like to keep it in safe shooting order.

Any help appreciated...