Like John said make sure the liner counterbore is spotless clean and the O-ring roove as well. We used to use a good wire wheel on a die grinder to clean out the groove and counterbore as well as the deck of the block. A gasket prep disk like they sell will remove metal and can upset the level of the deck surface is use too aggressively. Ohh and plug the holes over the lifters before cleaning and clean and blow out the headbolt holes when finished.
Ideally you should drop the liners in without o-rings and measure liner protrusion as mentioned previously. But if the counterbores look good and when you drop the liners in and you can feel they are above the deck surface buy catching them with your fingernails they are probably OK. I have the tooling to check that and would help ya if you were close by.