i've been running a 8 3/4 rear in my 70 dart 440 ,600 hp this year and no trouble yet. i changed from 4.89, to richmond 4.30 r&p. i put the rear together myself. car runs 11.0- 11.30 at 122 mph. foot brake only car and is lite weight but still around 3000- 3300 lbs. i don't abuse the rear and leave the line at 2500 and shift at 6400 rpm. the car has 10 1/2 in mt,s and they break loose alittle easing the strain on the rear somewhat. bashing off the line at 5500 on a trans- break, with 13 in or so tires hooked to the max, i don't think it would hold up. i don't race every weekend either. i have a complete dana 60 ready to put in, if i want, but i don't need it now. in fact it is for sale on ,diff- on this forum. heli301@comcast.net..........RON.