SB push rod legnth checker, how to

hello, 72 360,.. decked with unmiled 70-72 cc heads.. .039 head gasket.. not sure of the deck height.. any way i want to use stock style hyd rockers with shafts.. since my deck is decked id like to check the PR legnth.
i set number 1 cly TDC, rotor pointing to no 1 cly...anyway i adj the rod checker till all lash is gone right? then do i tighten another ??? or what? I am affriad to throw stock ones on.. what do u think?

camshat is a hyd comp cam, xe274h

Thanks