what size lift in back
 

I just bought a 99 gmc extended cab short bed new body style. The guy said it had the leveling keys up front and an add a leaf in the rear. The keys are turned all the way up and it does have shock extensions so im guessing there leveling keys. The rear sat higher in the rear so i took the add a leaf out now it sits way lower in the rear than the front. I was going to buy a block for the rear but dont know what size. Right now it has 1 1/2 block. The truck has 33s so I cant really cranks the t bars down. Should I just get another 1 1/2 block and stack it on the existing one for 3 inch? Or should I get a 2 inch and stack the 1 1/2 for 3 1/2?