I talked to Duane Wiebe about this, and he said to stay away from the 03 Springfield actions if I was going to build a sporter. He recommended an FN Mauser action. As luck would have it, I found an FN actioned Husqvarna rifle shortly afterwards. If I can scrape together the money, it may be the platform for this project. It's a bit more that a CZ-550 action, but I figure it probably is better machined than the CZ.
BTW, Mr. Wiebe said the Mannlicher-Schoenauer action could've been used, but the machine work would be quite costly.