James,
Handling and braking are great and handling for sure is much improved. My baseline was worn 205/70-14 tires, 230SL swaybar, Olsen springs, V8 vented front brakes, new Konis in back, old Bilsteins in front and adjustable brake bias valve. In general the improvement can be attributed to just having new tires. Some part of it can be attributed to the 60 series lower profile tire. Because my tires were worn I can't say for sure how much is based on just the tire profile. I can say the rear end is much tighter in turns. I used to blame the swing axle for any instability feeling in the rear during high speed turns. What I mean here is the lifting of the inside rear wheel during turns. I considered trying to fit a rear sway bar and installing limit straps on the rear axle. With this setup I can honestly say I was wrong. The swing axle wasn't the major factor causing my instability problem. The car is now very flat and stable when dmaking high speed turns. It's great! I like the tires very much. I can not get these tires to squeal. They are literally glued to the road surface.
I'm sure Joe and others would tell you that handling improvements involve brakes, supension and tires. Until making this change I was not getting the full benefit and usage of the suspension upgrades. I now feel they work together in a balanced way.