67-76 floor into a 65...

I have a '67 2 door sedan that I'm putting a full AMD floor in. I'm going to split the floor right over the center of the torsion bar crossmember and stitch it back together there. It will be invisible from underneath...

That’s what I would do, too.
I would also keep the structure and support of the old crossmember but just add a piece above it to attach to the floor.