Ribbed block here. The ribs don't seem located or sized for any particular structural purpose so the thread makes sense. Seems like a tedious effort for just noting a different casting group and slight change in metalurgy.
It's interesting some of the stuff they use to cast into engine blocks. 390s and 428s with a 352 number or 66 427 cast in. I was surprised when I pulled the 4-bolt 427 Hi-Per #321 block out of my Corvette and found "Truck" cast in the back bellhousing area. I think foundry workers must have had a strange sense of humor.
