Did you talk to Bart at PPIR? He is very good with tires/brands/wearing, etc. If he said you needed new tires it might be due to other reasons then lack of tread.

Older material can start cupping on the groves, rubber might be old and hard, uneven wear due to age.

I will let Bart give the answer as he is the one that will either allow you to compete or send you home. Remember, this weekend is looking a little cooler and wetter then the past two rounds so having good tires is critical to staying up. If you can get tires before this weekend, I would definitely say do it.