Tire Bead problems of the 2000 Chevrolet Tahoe

The tires were checked and inflated to 39 psi before leaving home for the 112 mile trip. On the return trip after approx. A one hour stop the right rear tire blew after about 50 miles. The tire has an l shaped split about 12" long 3/4" down from the edge of the tread then a 90 degree turn and an opening all the way to the bead. The sidewall of the tire below the 12" split has the cord boby of the tire atached to it. The cord has separated from the tread portion and is hanging down inside the tire. The tread to bead split is completely open both plies of cord split at the same place. I no longer believe that these tires are safe. My gm dealer had two reported failures of this type of tire on the same day the other person said his tire failed in the same manner at 18,000 miles. Gm is willing to replace the tire with another firestone wilderness at, but I would like them to replace the tires with another brand. (dot number: w273 tiresize: p265/75r16).