Actually working on the Falcon!
As Roger (plowboy) suggested, I fit the '67 Mustang suspension to the Nova frame, after I'd ground off the Nova's engine mounts, lower control arm mounts, and the crossmember just behind the torque arm boxes. Worked great! I also had to slightly cut down the Nova chassis just behind the fuel cell, and remove the molded drivetrain hump to fit against the Falcon's interior tub.
Obviously there's still lots more to be sorted out, but it seems workable now!