Hello,

"15 to 30 dollars a set at most places these days."

I'm sorry, but I don't remember the sizes, but the Heli-Coil or
equivalent for the drain plug is twice the price of one for a spark plug
thread of the same diameter.  I matched the drain plug thread and paid
about $35 a few years back.  If you go with the spark plug thread, then
you could make a drain plug out out of an old spark plug.

I have also switched to paper washers.  I make a new one every time out
of the oil filter box.  The paper deforms to a good seal and locks the
plug so it doesn't have to be tightened very much.  If I had been doing
that from the beginning, I probably never would have stripped the oil
pan.

Thanks for listening,
Mike