I'd just look for the numeric size and ignore the alpha. I know what you mean about replacing good looking tires. The ones I took off the trailer looked perfect, but were 4 years old. I always cover them when not in use.
The first set the tire store got were 18 months old and I said no way. They ordered several sets because they said they couldn't request certain date codes. The ones that came in were right at the 6 month mark, so I took them.
They do seem to track a little better than the el cheapie tires that came with the trailer.
Good luck!