I forgot to include, when you put the Plug back in, remember to coat the threads with anti-seize lubricant. Also as an ADDENDUM:
After you get that sucker out, consider going to SlixSpring (Badman Bullets) for a brandy Knew Two Ewe solid BRASS mag plug!! That Brass Plug looks the big on the end of a '66. Super TRIX. Looks pretty good on a '73 too. Just not quite as good.