I think if there’s any doubt, you should probably replace them.
It’s relatively cheap insurance.

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1981 240D 4sp manual. Ivory White.

Yes, good advice I think. I have experienced two blowouts in my life when I was driving...one country highway (parents car back in the day) and one interstate with my 300D...no fun at all and *especially* harrowing on the interstate. Cheap insurance yes and some peace of mind, too.
Thank you.