After cutting out the quarter, I found more rust (surprise!) in the rocker and below the quarter window. I cut it out, and hand made part of it as well as cut out parts of the rocker from the '68 in the yard.
Then I made up the bottoms of the outer wheel tub to weld the replacement quarter to.
Today a friend and I fitted the new quarter to the body and used panel adhesive along the top side. With a 3 1/2 minute bonding time, there's not much room for error!