About a month ago I cruised down to Tuscon on my 83 sd and I couldn't get it above 65 comfortably. It had the standard 14's on.

I put 15's on from a 87 420 sel, I was driving 80 today around Phoenix not even thinking about it. Freakin Awsome. Ofcourse I have been doing other things to the car to help the cause. This next weekend I am replacing the upper control arms for heck of it.