8 1/4 axle inspection.

Gonna open it up tomorrow. I got an bearing kit coming from oreilly's. If I need it it will be here Saturday. If I don't need it I can return it. One thing I looked for the yellow paint for checking gears and the parts counters people looked at me like I was asking for raw uranium. I have some white and red grease I can try. I also did find some prussian blue. I have a homemade carrier bearing adjuster. Another question how long should I make the shafts? Is 3' about right? Also my 8 3/4 axle is in the works. Having a housing narrowed soon. One other question, what size is the pinion nut? Thanks and wish me luck.