you'll want to take one cylinder ex/in spring pair off before you put the heads on, then do all your checking. if you use a pushrod checker with the roller springs installed you'll never get a reading cause the checker with collapse and be unuseable forevermore. i just grabbed 3 or 4 of your lifters and they are not going to collapse, they are still filled with
oil so you will not need to take them apart.
the heads do have hyd roller springs and not solid roller springs?