BuckeyeBlitz89-
I hope you don't mind my replying to your post above and also extending my reply to your PM to me of a couple of days ago.
As I stated in the PM, I planned to ask my knowledgeable gunsmith about the Rhinelard Arms conversion kit, and its possible application in building a 450B rifle.
The conversion kit solves a problem that I tried to describe in the recent thread on building a 450B rifle based on the vz24 action:
Mauser 98 VZ24 Build. The problem there was one of proper headspacing. That is, the new barrel as described there needs to be drawn up against the face of the internal receiver ring. The Rhineland kit solves that problem by ignoring the internal ring and deriving its spacing from the front face of the receiver. This is essentially how the current Savage rifles accommodate barrel swaps.
However, there is a potential problem. The threaded barrel stub is short, and Mauser threads are pretty coarse. So, when the barrel is screwed into the action, there is likely to be a relatively large degree of wobble between the action and barrel. The regular Mauser installation involves drawing the barrel up tightly against the inner receiver ring, which eliminates the wobble and squares the barrel with the receiver axis. In the Rhineland kit, the barrel is snugged into the receiver with the external lock ring, which butts against the front face of the receiver ring. The difficulty with this system is that the front of the receiver ring may not be square with the action, so that the barrel bore is not aligned with the axis of the receiver. The barrel may point in some random direction. Certainly a misalignment between the barrel and the receiver will not help accuracy.
The alignment problem might be solved by truing and squaring the face of the receiver, but this is not a trivial project and requires some careful lathe work. (It's possible that the Rhineland Arms persons have solved this problem. It's also possible I have misunderstood the nature of their kit installation.)
In the conversion, you also have to consider what sighting system you plan to use. Drilling and tapping the receiver for scope mounts can be simple for a gunsmith with the proper tooling. It can also be difficult if the receiver is hardened, requiring spot annealing. If you decide on a scope, you will also need to modify the bolt handle to clear the scope, and in addition install a low-mount safety.
The same problem of a hard receiver will show up if you wish to install a receiver sight, possibly avoiding the bolt handle and safety problems. However, with a receiver sight you also have to plan to install a front sight, which will almost certainly require a ramp.
All of this work can get pricey, beyond the initial cost of the kit and the receiver.
Whatever you decide, keep us informed here.
Good luck.
--Bob