You got to get it to squat and transfer that weight, also your rake is working against you...

I know this is apples to oranges but when I had Caltracs on my QC Ram they worked best without pre-load to get the rear end to squat. Unlike a car your truck is crazy front heavy and with the long wheelbase your front end is not going to pull up with a pre-loaded rear suspension.

Get it to transfer the weight and get off the line, you have much much faster times in it! Low low 10's with ease...