if you check with the last paragraph above yours i said it was a Ho72 rear.the rear is a GM unit.if you check with the factory chevrolet options book,on 30 series truck,page 189 middle of page......R_90 option 18"tires and wheels,heavy suspension and 350 -4brl carb.4spd tranmission and brake warning lite delete(?) truck.6.17 only gear ratio avaible for this truck.only option was a turbo 400 tranny. there was a option R_99 whish is exact same truck but with 19.5 wheels.And it is raced every week end and does not brake the rear.other depts are runnig a dana 80 and braking the axles.
