difference between a 742 and a 489?

My 69 Super Bee came with the 742 case{factory stock} and the only thing that ever broke in it was a set of Zoom 4:56's/ Snapped the pinion gear at the front bearing with a 6 grand jump at the starting line. :-) Damn thing would lift the left front about 1 inch off the ground with that hole shot. :-D OH yeah also had 9 inch slicks on it too!

Jim