info and links courtesy of tomustang
http://www.miracerros.com/mustang/springs_calcs.htm
The table below lists some OEM and aftermarket spring rates and the approximate drops they will give if installed on
94+ Mustang.
<TABLE WIDTH=640 ALIGN=CENTER BORDER=1>
<TR><TH> </TH><TH> Comment or </TH><TH> Rate (lb/in) </TH><TH>Rate (lb/in)</TH><TH colspan=2> Drop (in.)</TH></TR>
<TR><TH> </TH><TH> Part No. </TH><TH> front </TH><TH>rear</TH><TH>front</TH><TH>rear</TH></TH></TR>
<TR><TD>Ford Motorsports B </TD><TD> M-5300-B </TD><TD> 425-530 </TD><TD> 200-300</TD><TD> 1.50 </TD><TD> 0.75 </TD></TR>
<TR><TD>Ford Motorsports C </TD><TD> M-5300-C </TD><TD> 650 </TD><TD> 200-300</TD><TD> 1.50 </TD><TD> 0.75 </TD></TR>
<TR><TD>Ford Motorsports F </TD><TD> M-5300-F </TD><TD> 460-570 </TD><TD> 200-250</TD><TD> 1.50 </TD><TD> 1.50 </TD></TR>
<TR><TD>Ford Motorsports G (convertible)</TD><TD> M-5300-G </TD><TD> 460-570 </TD><TD> 170-310</TD><TD> 1.50 </TD><TD> 1.50 </TD></TR>
<TR><TD>Ford Motorsports R </TD><TD> M-5300-R </TD><TD> 700-850 </TD><TD> 200-260</TD><TD> </TD><TD> </TD></TR>
<TR><TD>
Eibach ProKit </TD><TD> </TD><TD> 425-530 </TD><TD> 200-300</TD><TD> 1.50 </TD><TD> 1.50 </TD></TR>
<TR><TD>Eibach Sportline </TD><TD> </TD><TD> 425-630 </TD><TD> 140-295 </TD><TD> 2.00 </TD><TD> 2.00 </TD></TR>
<TR><TD>Eibach Racekit </TD><TD> </TD><TD> 700-850 </TD><TD> 200-260</TD><TD> </TD><TD> </TD></TR>
<TR><TD>Jamex Sportsprings </TD><TD> </TD><TD> 425-450 </TD><TD> 180-225</TD><TD> 1.50 </TD><TD> 1.50 </TD></TR>
<TR><TD>2000 Mustang GT </TD><TD> OEM </TD><TD> 450 </TD><TD> 210 </TD><TD> </TD><TD> </TD></TR>
<TR><TD>2001 Bullitt </TD><TD> OEM </TD><TD> 600 </TD><TD> 250 </TD><TD> 0.75 </TD><TD> 0.75 </TD></TR>
<TR><TD>2003 Mach 1 </TD><TD> OEM </TD><TD> 600 </TD><TD> 250 </TD><TD> 0.75 </TD><TD> 0.75 </TD></TR>
<TR><TD>2000 SVT Cobra R </TD><TD> Eibach </TD><TD> 800 </TD><TD> 750 (IRS) </TD><TD> </TD><TD> </TD></TR>
<TR><TD>2001 SVT Cobra </TD><TD> OEM </TD><TD> 500 </TD><TD> 470 (IRS) </TD><TD> </TD><TD> </TD></TR>
<TR><TD>2003 SVT Cobra </TD><TD> OEM </TD><TD> 600 </TD><TD> 600 (IRS) </TD><TD> </TD><TD> </TD></TR>
<TR><TD>2003 SVT Cobra (convertible) </TD><TD> OEM </TD><TD> 500 </TD><TD> 470 (IRS) </TD><TD> </TD><TD> </TD></TR>
<TR><TD>H&R Sport </TD><TD> </TD><TD> 490-575 </TD><TD> 250-285</TD><TD> 1.60 </TD><TD> 1.50 </TD></TR>
<TR><TD>H&R Super Sport </TD><TD> </TD><TD> 700-760 </TD><TD> 275-300</TD><TD> 1.75 </TD><TD> 1.60 </TD></TR>
<TR><TD>H&R Race </TD><TD> </TD><TD> 750-850 </TD><TD> 260-280</TD><TD> 1.25 </TD><TD> 1.00 </TD></TR>
<TR><TD>H&R Super Race </TD><TD> </TD><TD> 950-1050 </TD><TD> 260-300</TD><TD> 1.25 </TD><TD> 1.25 </TD></TR>
<TR><TD>Progress </TD><TD> </TD><TD> 580 </TD><TD> 250-300</TD><TD> 1.75 </TD><TD> 1.75 </TD></TR>
<TR><TD>Steeda Sport </TD><TD> </TD><TD> 650 </TD><TD> 200-250 </TD><TD> 1.25 </TD><TD> 1.25 </TD></TR>
<TR><TD>Steeda Competition</TD><TD> </TD><TD> 750-850 </TD><TD> 250 </TD><TD> 1.25 </TD><TD> 1.25 </TD></TR>
<TR><TD>Steeda Full Competition [front only] </TD><TD> </TD><TD> 850-1050 </TD><TD> N/A </TD><TD> 1.50 </TD><TD> N/A </TD>
</TR></TABLE>
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<TABLE WIDTH=640 ALIGN=CENTER>
<TR>
<P>
</TD>
</TABLE>
2003-04 Ford Mustang Mach 1
Front Springs 600 lb unique linear rate
Stabilizer Bar 26.5 mm (1.04 in.) solid
Rear Springs 250 lb unique linear rate
Stabilizer Bar 23 mm solid (.905 in.) solid
1999-2004 Ford Mustang GT
Front Springs 450 lbs./in. linear
Stabilizer Bar 28-26.5 mm (1.04 in.) solid
Rear Springs 210 lbs./in. linear
Stabilizer Bar 24-23 mm (.905 in.) tubular
(1999-04 Bars claimed to be different thru years)
2001 Ford Mustang Bullit
Front Springs 600 lb linear
Stabilizer Bar 26.5mm tubular
Rear Springs 250 lb/in. linear
Stabilizer Bar 21 mm tubular
1999-02 Ford Mustang Cobra
Front Springs 500 lb./in
Stabilizer Bar 28mm
Rear Springs 470 lb./in.
Stabilizer Bar 26mm
2003-04 Ford Mustang Cobra
Front Springs 600 lb./in.
Stabilizer Bar 29mm
Rear Springs 600 lb./in.
Stabilizer Bar 26mm
1996-1998 Ford Mustang Cobra
Front Springs 400-505 lb./in. Varible
Stabilizer Bar 29mm
Rear Springs 165-265 lb./in.
Stabilizer Bar 27mm
1996-1998 Ford Mustang GT
Front Springs 400-505 lb./in. Varible
Stabilizer Bar 30mm
Rear Springs 165-265 lb./in. Varible
Stabilizer Bar 24mm
2000 Ford Mustang Cobra R
Front Springs 800 lb./in.
Stabilizer Bar 28mm
Rear Springs 750 lb./in.
Stabilizer Bar 26mm
FRPP C Springs
Front Springs 650 lb/in.
Rear Springs 200-300 lb/in.