Ok, my project keeps getting more expensive but such is life. I'm thinking of going from 3.73 to 4.11 or lower. What do I look for when searching for a shop to do the job? What would the total cost be for a gm 10 bolt (front and rear)? The previous owner told me that the rear was just rebuilt although there is chalk on the rear diff that says "89" I have a 1990 sub. Nothing leaks, do I have to replace anything other than the ring and pinion? What brand of gears are at least as good as GM originals? How much. Thanks.