Springs for 240sx help

I was wondering if these Tanabe springs are good. and I was also wondering how low 30-40mm and 15-25mm would be i tried to measure it with my ruler but then when i measured my front bumper would of hit the ground. Did I measure it wrong. Please reply back Thanks.



Click these link below and tell me if these are good
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33586&item=2424075614

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33586&item=2424810426