headlight bucket

I got a 53 chevy pickup. I was working on one of the fenders yesterday and was going to put in the headlight bucket but it wouldn't fit. They came with the trk years ago when I bought it and I assumed they were the right ones. They are too big to fit in fender but yet the chrome ring seems to fit. Brothers sales them new but it says you need to use your original towers. What are they talking about, original towers? Any help, thanks!