Some say to not use a spacer between the nut and tapered stud. The reason is, this repositions the front suspension relative to the chassis (actually, it changes the Instant Roll Center), altering the handling. Special ball joints with longer (or shorter) tapers are available to do exactly this, at extra cost. They are routinely used in dirt track racing. The upper rear ball joint Instant Roll Center usually does not affect handling that much. The effect is more noticable on both ends as cornering speed increases. I say, try it- depending on how you drive, you may actually prefer the geometry this way, or not notice it at all. A decade or two ago I adapted 67-89 Chrysler-type upper ball joints to our Pantera (same taper) and had to do what to me was minor machining on the tapers to adjust all six to my liking. They're still on our car. Good luck.