Danny D. wrote, on Wed, 17 Dec 2014 18:02:44 +0000:

If the plugs do just pull straight out, this will give me
the leverage, minimizing the risk to the "wire" from the
tremendous force that is needed.

BTW, the plugs were surprisingly in great shape.
https://c4.staticflickr.com/8/7534/1...b9347cb2_b.jpg

What matters to a plug, first and foremost, is a sharp edge,
which concentrates lines of force. The central electrode
was still (almost) as sharp as new.

What matters next is the gap, which was still around 30
thousandths of an inch.

The central insulator was carbon'd up, which is to be
expected, and not at all greasy or damaged.

Overall, there was no reason to replace the plugs, but,
I replaced them anyway since I already had them in hand.