13.9 .    
I have slicks. I just never put them on this car yet.  I had them from my Lumina days so I think I'll be ok in that department.    
I had the mustang bullitts on the car the last time at the track. I just found out those things weigh liked 50 lbs a piece with the tire.  My stock rim is what I'm pimping now  and they weigh around 40ish each.   
I just put on an i/c on.  I was running like 12 degrees of timing and still getting KR with a 10.5 a/f .    
Now I'm around 11.5ish and got my timing up to 18 and stock tires.     
Once I get that tuned in I'll throw a smaller pulley on it (looking for a cheap Modular pulley setup with a 3.2) at the track and see what happens.    
with the tire change, i/c, a/f fix, and timing upping.. I shouldn't get anything slower than a 13.5.    
We'll see .