Is it possible to use XCode6 beta with an IOS 7.1 SDK? The new tools are much nicer but I need to build for IOS7
Yes. 1. First download 7.1 SDK - XCode6Beta > Preferences > Downloads > iOS 7.1 Simulator.
Note: XCode6-Beta can co-exist with regular XCode (XCode 5.x). But when you download iOS 7.1 Simulator, it actually gets downloaded into XCode 5's path!! (probably a bug).
Now if you go to Project's Build Settings, Base SDK, you will see 7.1 along with 8.0.
Enjoy!