[font=Times New Roman]I'm new to all of this, as you can tell, and seeking information on building my own from scratch.  Does anyone have information on who provides the best of the 80/20 Billet Lower Receivers, and how do I know if it will work with the 7.62/.308?  So many questions, and I'm sure that all of you have the answers to guide me in the right direction.[/font=Times New Roman]

The AR15 and AR10  are two totally different receivers. The AR10 receiver is .308.
There are two basic AR10 patterns, the DPMS and the Armalite. Some parts are different between the two and will not interchange. The vast majority of what you see out there for sale is DPMS pattern, so it is the logical choice to go with.
I would suggest a particular brand, but I work for them, so I will not.

Start here.

Look around the tech forums, do a lot of reading.  Going to need more specific questions to give specific answers.