Re: AR-10 build ?s
You will need to use a Armalite Style upper. I have not tracked with a AR10/308 world lately so I don't know if they are the only ones building that style or not.
You need to fill in a lot more info before anyone can help you.
Budget
Use
Accuracy expectations
Building skills and understanding
As for me, I only see the need for a AR10/308 for precision work inside 700 yards. For that I would not choose anything but a GAP-10.