Toodie Jane wrote on chowhound:
I knew an old cowboy who worked a large ranch near Woodlake in the 50's and did deep-pit bbq's for them. He's gone now, but he described the process exactly as oerdin below. Build a big fire in a bigger pit, using live oak. Let it burn to coals, place rocks over coals to heat, cover with chicken wire (with shovel handles threaded through the ends) and wet burlap sacks, place the meat, more burlap sacks, then finally a foot or so of soil. They let it go about 8-10 hours for a side of beef, about 8 hours for a whole piglet. The wire length was long enough to extend out of the pit, and was used by three or four guys to heft the meat out of the pit once the soil and top burlap bags had been removed.

So I assume you will get one giant piece of chuck.