Honestly, if it was me putting one together for CQB, I'd go with a 12.5" barrel and either the latest flavor of Vltor's clubfoot stock or the Magpul UBR. Probably the Magpul for the consistent cheek weld. At that barrel length, twist rate wouldn't even be a concern. I'd go with a 1:10 poly bore like Noveske's, assuming I could find one. Daniel Defense makes a nice rail for the AR10, so I'd probably go with that.
There is absolutely nothing wrong with having the stock barrel cut and re-threaded, and might save you some cash if that's the route you want to go.
There is absolutely nothing wrong with having the stock barrel cut and re-threaded, and might save you some cash if that's the route you want to go.