Jay, I don`t run tubes with either car. Maybe I have just been lucky, but since I stopped using tubes almost 20 years ago, I have found that by using the old dish soap trick on the inside of the sidewalls, both the Hoosiers and M/T slicks tend to hold air very well. The Fairmont has much bigger slicks, currently 13x31, have used 14x32s for many years, and on a 14" wide wheel, I normally run 10-10 1/2 psi, the Mustang usually has either 9x29 Hoosiers, or 9x29 1/2 M/Ts on either 8 or 9" wide wheels, at 12-12 12psi. Funny thing is, back when I ran a C6 (with transbrake), I had to run much less air pressure to make the car hook well, as low as 6 or 6 1/2 psi with the 14x32s.The natural rubber M/T tubes I was using were quite heavy, much heavier than a normal tube, close to 10 lbs each. I would balance the slicks at work, and after a few races, I would get a vibration, that got more severe as I made more runs. I checked the balance again, and the imbalance had gotten way off. It appears that the tubes had been moving around inside the slick, and wadding up, which put the tire out of balance.So after a while, I wound up having to remove the rear wheels, let all the air out, and then shake the slicks with the wheels laying flat on the tire machine, which would allow the tube to "flow out" evenly, so that when it was aired up again, it would be back into a balanced condition again. But I had to go thru this routine about every 20-25 passes. After talking to several Stock and Super Stock racers, it was almost unanimous to run tubeless. With new slicks, I normally can let the car sit the usual 2 weeks between races with no need to air the slicks up, the Hoosiers on the Mustang normally hold air for 2 months of sitting! Over the years, I have had some slicks lose a couple of pounds over 48 hours, but normally quite a bit longer. One thing II did notice, was if you dismounted the tires, and re mounted them, they normally held pressure less well than before. I`m guessing the stress of breaking down the sidewall beads caused some minor sidewall damage, causing air to escape easier thru the sidewalls. So I normally install new slicks, and avoid dismounting them untl they are due for replacement.