I don't know if this is always the case with slant 6 engines, but mine has an aluminum retainer for the rear main seal. One of the two oil pan bolts that attach to this retainer had stripped out the threads in the soft aluminum. Fortunately, the bolt is only 1" long and the threads go about 2" into the retainer, so only half of them are actually stripped. I simply chased out the remnants of the stripped threads and made sure the others were cleaned out with the proper 5/16" x 18 tap. All you have to do then is buy a longer bolt that will catch the lower threads but not bottom out in the hole. Of course, another option is drilling out the hole and installing a helicoil. I did not have the special tools necessary to do that (21/64" bit - special helicoil tap - helicoil installation tool), and did not want to spend the $20 it would cost for the repair kit. Not only that, I had just installed the oil pan with a new gasket set and did not want to spend $9 for another and go through removing and reinstalling the pan, just for one little bolt.

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There's a difference between ignorance and stupidity.
Ignorance is not knowing any better.
Stupidity is knowing, yet doing it anyway.