8 3/4 is this correct

Being a tad over using green bearings won't hurt.
But if going with OEM bearings then things need to be righter because you are going to be adjusting the end play by thousands of an inch. So if one axle tubes is an 1/4 off of the other things are not going to work so good.
Dr. Diff is the man to work with. He will do you right.