Ok, tbh,
I've done this type of "conversionism"
to two JCM 800 vertical imput combo's.
Yeah, it was cool..but not worth the time
and money in the end.
I've learned...hold out for the head.
I say, pull those BlackM'fer's out of there,
swipe up some 65's or in the vintagey' speaker
realm (75's, etc) and install those in there.
And since it's squeaky clean chassis wise
you can pull back what you invested in it.
But there's one more thang'...
You got J.Lo's ass sitting home waiting on you
when you come back home from selling the
amplifier to the next dude.
HUSTLE.