My comments on using oversize plugs:
1. Not the purist's way to do it, but it's the easiest and quickest fix.
2. Remove the washer, and put axle grease on the threads of the OS plug (you want to get an M14-1.5 OS plug) before you use it to cut the new threads. Removing the washer allows you to screw the plug in and cut the new threads beyond the point of compressing the washer and sealing. That way, after you're done cutting the threads and re-install the plug with a washer, you *know* that when it tightens, it's because it's compressing the washer and not because the threads got tight when it hit the unthreaded area of the hole. The grease will capture any chips of aluminum form the newly cut threads. After cutting the threads, remove the plug and *thoroughly* clean the grease and *ALL* chips from the threads and cuts in the plug. Also - take a brand new can of brake parts cleaner with the red straw, stick the straw into the drain hole at least a couple of inches, and spray brake parts cleaner into the pan full blast, pause every once in a while to let it come streaming out of the drain hole - that's to hopefully wash out any chips that might have escaped. Use the entire can.
3. Throw away the washer that came with the plug and go to Lowes and buy a common garden hose washer (perfect size) and use it instead. Why? Because (a) the OS plug will probably not thread in perfectly straight (trust me on that - if it goes in straight, it is pure luck) and will not seal when it tries to seat to the pan because (b) the company that makes the plug is stupid and supplies a hard washer with the plug, so it can't seal if the new threads (and therefore the plug) are tilted at all - and oil will continually drip. The garden hose washer is much softer and will squish a little to seal perfectly, even with a slightly tilted plug.
4. Only tighten the plug enough to seal it because the newly formed threads are nowhere near complete - they are much weaker than the original factory threads that already stripped. (If you use the hard washer supplied with the OS plug and the plug is tilted at all and you try to seal it by tightening it more, you will strip the new threads before the plug seals - guaranteed.)
5. Think long and hard before letting anyone change the oil once you install the OS plug (because the threads are even weaker than the original factory threads).
Have a nice day.