Who's building them ? Driveline Tech here in Portland does awesome work and you can get both shafts done for what some other HIGHly acclaimed shops charge. go with .250" if you plan on using your shafts as sliders. good call on swapping cv from front to rear AND BONUS POINTS FOR AT LEAST TRYING TO SEARCH!!!1 good noob.

http://www.drivelinetech.com/default.php