My experience unfortunately is limited to the 82 I have. I've tried and never found any marks or arrows. In the end, and especially since you just can't know what evil (well intentioned or not) has been done before, balancing it IMHO is the way to go. Still, mark it before you take it out. Then, clean it up and replace the center support complete. When you take it to a competent shop (and I'd do some searching and ask around - racing affectionados are a good source) ask them to see how balanced it was in the position it WAS in also. Then, you have the added knowledge that it was out of balance, and if so, how much. Pick their brains a bit, it's almost always worth it.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.