I bought parts for the 85SD but didn't think about springs. Is the experience that they need to be replaced at 200,000 mi and that OE replacements are the way to go?

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.