This is the car that GN uses to illustrate their handling kit. It also has, as they recommend, the "Arning/Shelby drop". I notice your example has the Traction Masters, which they recommend.
That G-N car is a little high in the back for me...I would want it perfectly level...i think that Emberglo car is either level or slightly lower in the back...what do you think?
That G-N does sit like 2+2GT's car...it sits just like a GT-350...it looks great on a 2+2...very sporty...but I would rather keep a coupe level.
I agree that the most effective change cost $0. Do the Shelby drop.
I used drop springs with a taller insulator on top. I dont see how roller perches will do anything.
Get some tie rod ends and ball joints from anywhere and a 1" sway bar. You will love it.
Your steering box is the same quick ratio as the GT. Mine takes a little effort but its comfortable(without power assist).
Roller perches improve the spring actions up and down motion. There is not much movement there but it is a difference. I was a disbeliever in them until I received a set and swapped them on the car. The car had brand new stock spring perches with less than a couple thousand miles on them. I swapped them to the roller perches and it was an amazing difference.
The biggest change I could see was when crossing railroad tracks. With the stock perches, there was a bit of a drift if the tracks crossed the street at an angle. With the roller perches, the car had no drift, even at increased speeds. I also found the cornering was better. The front tires seemed to stay planted on the road better.
If you compared the action of the shaft on the two units, you can see the improved action. On the stock unit, it is nearly impossible to rotate the shaft in the rubber bushing. With the roller unit, the shaft spins freely with a twist of your fingers. This is the part that must move as the spring travels up and down. Less resistance equals smoother spring action which equals a smoother ride and better handling.