Hi,
I have P205/75R14 radials on my 57 and like everybody else they would occasionally rub the skirts. Exit ramps off the expressway were guaranteed to cause a rub UNTIL I installed new front and rear sway bars. I got the Hotchkis Suspension package designed specifically for the early T-Birds which can be purchased from a number of places. Great kit, easy to install. Only two small holes have to be drilled in the rear frame cross member that no one will ever see. Rubbing the skirts is no longer an issue and the car handles like a modern car. I highly recommend the kit. I found that it tightens up the whole suspension. I only wish I had put them on years ago.
Good luck
Doug