Wow - with those temps you might consider leaving the far end open (wire), or at least framing in BIG screened (hardware clothed) windows most of the way around, since your birds will be battling heat. You might do a search on open air coops.
Personally, I wouldn't want a dirt floor unless you...
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That's what I needed, and yes the will be free ranged at least 8 hours a day
You have that lovely coop/run area already framed out and roofed. Maybe consider walling in part of that to create your housing, and then add run space, unroofed. That would probably be your cheapest option...