subframe bushing tape...

[JohnZ]

The tape in the photos appears to have been applied to the underbody, not to secure the cushions to the subframe; I'd guess Fisher Body applied it at the rear mount bolt hole locations to keep water out of the body during their 3-minute on-line water test in the Trim Shop, which had spray nozzles under the body as well as on the outside. They also had large foam clamp-on masks that covered the heater and blower openings, steering column openings, and floor shift openings, as all of those parts were installed later by Chevrolet.