I agree with you. They don't handle worth a crap. The chassis are flimsy tuna cans. Turn into a corner at speed and you can feel the entire car flop from side to side like it has a fat lady in the trunk rolling around. But they can be made to handle very well even with the live rear axle. It just takes a few modifications and some money. But, consider this... Back in the day when these cars came out you could spend $20k on a Stang and throw $10k worth of
suspension at it and blow away a $30k Vette with EASE. I did it with my '90 with far less.
It's us die hard Mustang fans that are to blame that the Mustang doesn't handle well, because we are the ones trying to race these Vettes and BMW's. That's not what Ford intended these cars to do. So in my opinion Ford did it right all along. They built a cheap muscle car and left it up to the customer to make it the car THEY wanted it to be. I believe that has been a big plus to the Mustang's appeal all along. Take a look at every 'Stang on the road. Every one of them is different. Some go to the drag strip. Some go Autocrossing. Some are driven by 18 year old kids, and some by little old ladies. Bullitt on here is from Saudi Arabia. Then there is Ivan from Russia. This simply amazes me that these cars are being modified all around the world, by every walk of human life. Name another single car on the planet like it?
My wife is very finicky about the cars she buys. She won't buy one with a dent, dirty interior, or that is more than 5 years old. She won't buy one that makes any engine noise or one that has too many miles. She knows just about as much about cars as I do. I let her drive my '94 vert home from the dealership where I bought it so she could see if she liked driving a convertible. This was three weeks ago. Three days ago she bought a yellow 2001 V6 Mustang that has a dent or ding on every single panel on the car. The interior has pieces broken and has dirt everywhere. And when you start it the lifters tick for the first minute or so. To top it off it has nearly 190k miles on it. The Mustang put a spell on her just as it did me 27 years ago when I bought my '65. Believe me when I say I cannot figure out what driving my car did to my wife. But I like it.
You are correct that
suspension should come second. Chassis stiffening should be the very first thing done to any Mustang. I was just saying the ride height of the Mustang kills it in the corners. The Mustang sits way too high. In my opinion, the biggest difference you are going to notice is swapping out the springs and shocks and getting the ride height down. All of the other things will make a difference. But none will be felt as much as springs and shocks.
Here is the order I plan to install everything (my car came with a strut tower and k-member brace and Ford C springs and Tokico shocks and struts)...
1. Sub-frame connectors
2. Rear shock tower brace
3. Sway bars
4. Koni struts and shocks and coil-overs all around
5. Rear
control arms and
panhard bar
6. Tubular K-member and front
control arms
Then I might strat on the engine mods, if I ever do.