DC,
Absolutely nothing other than fit a standard length action with nil alterations other than bolt face and some rail massaging ... but then what will a 404Jeffery do that a 416Rigby, 416Ruger or 416Taylor wont?

Just another option given that he threw in that's he'd considered a 425Express ... which I also think can be built pretty damn cheaply ... more so than the 404Jeffery.
Cheers...
Con