strange noise after rear drop

[SnS C10]

ok everyone so today i lowered the rear of my 73 lwb c10. it has a 454 with two piece drive shaft. i pull the 2 leaf springs form each side so now it has a total of 3 on each side. i took the two shortest ones out. now, the bump stops are only half inch from the frame rails. when i take off somewhat hard, just enough to open the secondaries, there is a horrible vibration feeling/noise coming from the rear end. my guess is the driveshaft angle is off what do you guys think? can i fix this by dropping the front a little more or do i need to add one leaf in back? thanks for looking