The difference between a 454 Casull and a Walker by Uberti is in the amount of several hundred more dollars spent on the Casull production.
Those of us that shoot the Italian imports will generally agree that a box stock gun is a project waiting to happen. They can be made to run as smoothly and efficiently as a modern gun but they do take some work.
If the pieces and parts are all there then you have a pleasant project ahead of you toward the most powerful handgun issued to any armed force up to the advent of the 357 mag.
It is not recommended but a Walker with a full 60 grs of FFg behind a 457 round ball is an event to be witnessed.