You can get the Dakota arms blanks from Brownells. The ones they sell are already cut for aftermarket barrel contours but if you do so comparison you might be able to get one then just need to do some hand fitting. They are decent looking ribs, though kind of basic.

Bill

P.S.- 338x74R do you have a rifle so chambered? If so what and what kind of ballistics do you get from the gun. I've long been interested in this wildcat but haven't yet gotten around to making myself one.