Case differance's

There's no 349 case. You probably read it wrong. The only cases in 72 were 741 and 489's. The 489 case is plenty strong for your power level. That's what I'm running behind my 408 that's making over 500 lbs ft of torque and about 475 hp. Only problem I ever had was sheared gear teeth. I've seen more teeth sheared off the ring gear than broken pinion shafts