12 bolt rear
You already have 33 spline axles aftermarket because 12 bolts never came with 33 stock. SO they must be aftermarket. you have c-clip elim kit - again if you do (which I doubt you will) break an axle your safe again.
You have a spool again you can not get any better for what you are doing.
As I stated make sure your axle tube are weld to the cast center section...(stitch weld this if you doing it in the car or you will warp the axle tubes)
Main bearing caps would be the only upgrade if they are not already done.
GO racing and enjoy .
They only thing I worry about is that however set the rear end up did it correct and the back lash is in the .004-.007 range. A dial indicator with a magnetic base will tell you that measurement.
do not go over kill ...you have a good base rear use it. Jim