2003 Mach 1 OEM
Front Rate (lb/in) 600 Rear Rate (lb/in) 250 Front/rear drop from Gt is 0.75 (in.)
Both front and rear are (linear) on stock Mustangs
Example
(progressive)
Eibach ProKit Front Rate 425-530 Rear Rate 200-300 drop front/rear 1.50 (in.) from stock
You need to know what the 94 spring rates are!
Progressive Rate vs. Linear Rate Springs - A linear rate spring has a constant spring rating, no matter how much the spring is compressed, for example 600lb/in. This means that for every 600 pounds of pressure, there will be 1 inch of spring compression.
A progressive rate spring will have a variable spring rate, for example 425-630lb/in. This means that it may take 425 pounds for 1 inch of compression, but as the spring compresses more it will rise to as much as 630 pounds of pressure. To put it simply, the spring "progressively" gets stiffer as it is compressed.