What type of build are you planning? What caliber? What purpose?
Full disclosure, I’ve built a 260 Remington on a savage long action. It was a decent rifle. Nothing special. That’s about as much as you can guarantee.
It’s tough to do a remage build on a trued action because you generally open up the receiver threads a few thousandths when blueprinting. Then the fit may not even be safe, let alone precise. You could try the remage barrel on your factory action and see how you do. You could also have somebody dial in the action and just square up the action face, lugs, bolt lugs, and bolt face so at least all those surfaces are parallel. The thread fit on the remage stuff is usually a little sloppy (2B) anyway so it could help with any thread misalignment still there. That’s what I had done to my savage before I got my lathe and started learning.
I’ve done several builds on actions I’ve trued using a traditional tenon on the barrel but honestly I’m unsure how much accuracy it adds. I’ve got a lathe and know how so I generally do all that I know how to.
My honest advice to you is to find somebody who would do a good chamber job after truing your action, or look at a bighorn origin action if you want to do the remage route. Cost will be pretty similar for or a barreled action. I always ask myself this though: why don’t I hear of any benchrest shooters winning with savages? I know our game is not benchrest but accuracy is accuracy. You are stacking tolerances with a barrel nut that you aren’t with a custom.
All my builds with a cut rifled blank and a good setup/tenon/chambering job have shot sub 1/4 MOA with factory ammo off a bipod and rear bag. Any good builder should be able to get you sub half MOA or better. You may get it with a barrel nut and you may not.