I used the mancini connectors , welded them in, they were too short..as in the shoe that fits to the rear frame did not slide back enough so that you can weld the boxed/tube portion to the rear frame section.
I extended mine at the fronts so that I could weld the tube along with the shoe to the frame.
They made a HUGE difference, like crackedback said...jack lift the car at the corner and you notice right away...as well just taking hard turns...leaving the line....the car feel 10 times stiffer.
