can someone give me the diameter (and possibly free length) of the rear spring? tia.

 

bump

 

id = 5"
od = 6"
free length = 12"

 

Rear spring diameter is limited by the size of the upper pan that the upper spring seat sits in and the size of the upper spring seat itself.

Rear spring outside diameter is 5"

Inside diameter varies by wire diameter, 2003/2004 cars have slightly thinner wire diameters vs 2004.5-2008 cars. I measure 4 15/16" for a 2005 spring.

Free lengh 12 7/16"

If your after a aftermarket sub, go with Eibach ESS 5" OD. 11" and 9.5" free lengths both have a wide range of spring rates. Trickiest thing will be cutting just enough off one end of the spring to have a pig tail that will sit properly in the lower control arm. You can fab your own bushings to slip above the oem upper for a bit more height if you need to, up to +.6" can be done.