742 8-3/4 Sure Grip Rear

since you have the axles out --take your tape measure and extend it into the housing until you catch the end of the splines in your sure grip --this can be done -- now measure back to the face of your housing add 1/8 inch for bearing standout --- now measure the length of your axle from the spline end to the outside edge of your bearing -- compare that measurement to your housing measurement -- you should be within an 1/16 - 1/8 inch either longer ( preferred ) or shorter on your axle measurement for proper engagement of the splines.. measure both sides of your housing and your axles this way.