Your thread title "How important to measure" can be answered with. "It's very important to measure.". Most of the answers were basically somebody should do it. We have the correct mics in the shop and my Bud, the master tool and die maker is and expert. We measure every thing after tear down, then take what needs work to the machine shop and tell them what we want done. We trust our shop to order the needed engine kit to complete the job and we do some spot checking when we assemble the motor. All machine work we have spot checked over the last 11 years has been extremely well done. Our only problem we had with a machine shop was not vatting the blocks properly after the work. We no longer use them. One note, on any cylinder that has a noticeable ring grove has required boring and new pistons.