I believe the thinner of the two or less beefie, is the 87. ( the one on the Left in 1st pic )

I am also under the impression that they are supposed to be completely flat, with no bend or arch.( I though a bend in it was sign of wheel hitting something resulting it the metal giving alittle)

hope that helps ? 

Ask a forum and get ready for many opinions .......not sure who is the GURU on this topic .