rearend/suspension problems

I recently sold the 03 irs out of my 00gt and got a 96gt rearend in the deal.The rearend had steeda sport springs and steeda upper and lower control arms and tokico shocks,well after getting the rearend in the car it has the 70's stance,Its jacked up in the rear...Its higher than a stock gt..what would cause this problem...I have checked to make sure everything is in its place and tighened..Is there something im missing?Any help would be appreciated..

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It was the control arms,they were tightened up with the rearend hanging,so i took the springs out and loosened the control arms and jacked the rearend to normal ride hieght and tightened them back up and it fixed the problem