Look, with rare exception (that old Savage 310 for one) barrels are simply screwed into the receiver. To take them out, you unscrew them. To put in another, with the same thread... Screw it in. Now you do want to understand and "set" headspace correctly or it can blow up, easily... And do things to your head/face ... a butcher wouldn't want to look at.
Ruger #1's are barrelled this way. BUT besides the barrel there are other parts. I had a #3 once. As I recall there is an assembly under the barrel in the fore end that controls ejection. IF you go with another barrel contour, then you must fit this assembly back or give up "ejection" for "extraction??? Do you cut a groove in the bottom of the heavy barrel. Then there is the wood. It can be done. It is called "labor" and it is not free. Better work men usually have lots of work and charge more. Re-barrelling with the original contour is "chicken" but saves alot of explaining and charging and "you said the barrel cost... what is all this extra..." Gun Digest annual has a list of 'smiths that choose to advertise. Benchrest.com has another list of 'smiths. Some of the best, but slow and expensive... Your callllll... YOur bucks. luck.
