I use my finger nails, when there long enough, to judge the finish on the heads and blocks, if I feel the serations from the cutter on either the block or heads it is to rough for me I have had new Cometics MLS head gaskets on a new Hemi block leak before I found out they(Cometic MLS gaskets) need a RA finish of 50 or smoother to seal IHTHs Check for cracks real good