Old post, but since I'm a recent 78 TA owner I will chime in.
I bought a 78TA project back in May- it's a factory Martinique blue W72 4-speed TA with Hurst t-tops, but is a stripped, rolling cassis. I'm planning to do a pro touring- style build with this car, but keep the paint and bodywork stock for the most part. I plan to run 17" x 9" snowflakes on thia TA, so tire size is a concern to me as well.
I prefer to keep tire sizes the same front and back as well, for ease of rotation, spare tire replacement, etc. I have no desire to drop my car more than 1" either. 285/40s are 26" tall, but much wider than stock. I'm most likely going to run them all around, see where they rub. I have 275/40R18s on 18x 9s on my 72 Bird- those only rub at full lock, and I rarely need enough turning radius to put the wheels at full lock.
Geno