Which headers to get?

I have never had a 73 with something running in it, but I have had several 67-72 cars. They should be the same for fitment. All of them I had, I had the cheap Summit headers on and they fit good. The only thing they hit were the torsion bars and I was able to easily tweak them not to make contact. As long as your car does not sit low in the front, you will not have any trouble with ground clearance.