assuming the same retainer/locks are being used here... there is something wrong... Either your springs are mounted too low (stock is 1.72 inches from retainer to head) or your valves are LS1 blanks, which will be too tall.
LS1 blanks are common in rebuilt heads... all zzp ported heads use them. ZZP also sends out shims for the rockers on all of their heads as the LS1 blanks are taller, which will require a "taller" rocker to maintain correct geometry.