What specifically are you trying to build - for what purpose? Budget? Just to be clear, you want another 457 in addition to the one you already have, right?
If so, then you might consider getting on some stores' wait lists for a bare-bones 457 American in the synthetic stock (~$450) as an action donor and buy the other bits separately. I've read good things about Lilja drop-in barrels - I have been thinking about one of those for a CZ-455 I have laying around (same barrel for 455/457) in order to build an accurate light-weight (8.5 pounds or less) sporter. By "accurate" I mean comparable to my Vudoo and Rim-X. I'd build on the Rim-X, but the action by itself is just over two pounds in weight....