You using a split ball gauge and micrometer.

Sounds like your on the right track anyway and at the very least understanding the importance of the clearance. The old school marine truck engines seemed to run flawlesssly without marine prep however that was before any real power stated to come into play. Then again at least some if not several didn't even have oil coolers. I ran over 60 miles wot at 4,600 with no issues. Bone stock 78 boat. Water temps 50/60 deg.

Yes I do understand importance of clearances but wasn't sure what the "marine" standard was. Funny you should mention your truck engine. This year I was trying cams and home grown risers on a stock 310 7.4 Gen vi, I had a simple RPM to 02 deta log on it. 40 hours at plus 5000 RPM and 15 hours at 5500 RPM. I'm not saying it would live a long and happy life but it did live and was happy or did it live and I was happy 😊. Either way it was great data to take for the new build and learnt a lot about reversion why it happens and how to stop it.