The BFG Radial TA has been the classic muscle car tire for many years. When it first came out the letter style and size was a bit smaller. It had the right look at the right time and has just hung on as "Accepted" replacement for the old originals.
It has never been a great tire, but none of the white letter tires are really what I would call a great tire.......
Its popular mostly because it looks great and is good enough.
I have ran them along with some others.... They get you down the road about as well as any other white letter tire IMHO.
You need to realize, they are not High Performance tires. They are little more than a budget radial.