Try
http://www.coilsprings.com/ I got springs for my 65 catalina wagon. just told them the year make and I wanted a 1 inch lift and they said no problem . they already had the specs. I'm sure if you wanted 3 or 6 inches from stock that they would be able to do it. They did mine and shipped it to me for bout 160. and they ride smooth!!
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ALWAYS POWER!!!! ALWAYS PONTIAC!!!!
http://www.cardomain.com/id/habanero