Looking at an E body 70 challenger

You are going to have a heart attack when you see what original 15" ralley wheels are going for, the last set I seen for sale was $800.
My Challenger also came with 14", which are still on the car, but I got lucky and my cousin sold me a set of 15" cheap...He did not know what he had.
Where are the dates on the 15 inch wheels wanna see if original