How do you indentify 340 exhaust manifolds?

Thanks
I have a few sets of exhaust manifolds and just want to know how to tell if any are 340 manifolds? One set came off my car which is 72 the other two sets were givin to me?

Over the years, I have had a lot of sets of these. It used to be fun to walk through a salvage yard and pick them out of the pile for $15 each. I think I sold my last set for $475. IIRC, the part numbers are 2863549 and 2863553 for the good 68 to 70 ones.