Wouldn't the seats have already been in the car when the undercoating was applied , that was an operation I thought that was done when the car was pretty much fully assembled ? If this is the case that strip of tape on the floor wouldn't be like that ... but plants vary I guess as to when what was done ?

I remember a reference resto that was reundercoated , when the car was originally documented the seat bolts protruding thru the floor were wrapped with masking tape ?