One of the most important factor is that the roll center should be just above the ground. If a 4" ride height put the RC below the ground, you are going to have handling issue. Also, one must have enough suspension travel/shock travel to eliminate harsh jolts due to the bumpstop hitting. Talk to Mike Maier, located in Hayward. They are mustang specialist, but he knows how to design suspension.
Check this out.
https://lateral-g.net/forums/showthread.php4?t=23997
Cliff
70 Chevelle