what rear springs to get for and elcamino

I have and el camino that i currently are running the factory springs in The car sets at 27in from the ground to the fender well lip. I ordered some 14in 110lbs springs and acutally raised the car up about.5in so i took them out. the car weighs 1440 in the back so what springs are you guys running on the back of your el camino. I would like it to drop about and 1in to 1.5 because i think that this will help to with my 60ft which is only 1.68. My best 1/4 pass was 11.73 @ 116.09 so tell me what you think thanks Josh