90chevstepside
iPhone Repair Tech!
The "spring perch" is the flat part that the leaf springs sit on. The perch widths they specify are different bc the widths of each axle is different. No one quote me on this bc idk if it's right but I think the spring pad/perch width of a Dana 44 from a 77-79 ford is 32.5" that means there are 32.5 inches from the center of the left spring perch, to the center of the right. A newer ford axle is something like 36.5" or wider, meaning the perches are farther apart from each other. If you have an axle with really wide spring perches, and you put large wide tires on it, you'll rub the tires on the springs since they're so wide.
Clear as mud?
Clear as mud?