I believe the thread pitch on a 700 is 1&1/16x16 and the 70 pushfeeds were 1x16. Tenon length is longer on the Winchester too. Turning the diameter down on the Remington barrel may not completely clean up the old threads. I am sure someone has done it though.
Unless you have access to free machine work I can't imagine you would save much money over finding a push-feed 70 barrel.
