I can't speak for all vehicles or all plants back then,but from my experience,I have never seen an adhesive Tire tread decal on any Assembly line mounted tire.
Spare or axle mounted.
Most likely they were removed once they were assembled onto the rims,after they were static balanced,and a tread stencil was applied for specific model application callout.I have a very good 1967 16mm movie showing the entire Goodyear Tire plant process in sequence.
Tread Labels were applied for retailers purpose I believe.
