I did the oil cooler lines couple years ago. It sounds as though you were careful not to cross thread, this is good. I'd just loosen what you did up, "giggle it into alignment" ; "give it a good feel":, and re-tighten it where it feels best. You will feel where she wants to be.

Use a back up wrench and tighten snug. Back up wrench holds the thing you are tightening to. I don't think these have to be rock hard tight, just snug and a bit more.

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1982 300SD