Tony's old and doesn't have anything "hanging" anymore. It's shriveled up and blown away.
As for the trailing arms on a '73 - '87 truck, it could be done but the frame styles are different. The '73 - '87 frame is much flatter due to the design and leafspring rear suspension. On the trailing arm trucks, the frame is much higher so as to make the necessary room for the rear coils to fit in place and still have suspension travel. If the plan was to to do a custom frame back half with airbags, then adding the trailing arm suspension would be a matter of setting up your own geometry and airbag mounts.
Easy right?