I don't want to be a wet blanket, but how do you plan on installing that barrel? Do you have the proper frame wrenches and inserts? Have you verified they even work with the 8-shot N (G) frames? I'm not sure offhand but I don't know of any of the 8-shot N/G scandium frames that use crush fit barrels. So that's not how S&W would even attach the factory barrels. Aren't they all the 2-piece type with the main tensioning piece up front like a Dan Wesson?
Typically replacing the crush-fit barrel on an aluminum/scandium frame is a risky proposition even if everything else is in order. If you try to crush fit a steel N frame barrel onto a scandium G frame that's designed solely for a 2-piece barrel you're probably going to destroy that frame. There won't be any "sending it in" afterwards.
I don't want to dissuade people from taking on interesting projects but the fact that the L and N frame barrels were not interchangeable should probably be a red flag to slow this train down a bit.