How big of an issue is this gonna be

The only thing "WE" run 25-30 on is circle track engines that run 50 wt oil.
BUT...an observation...you need to be checking clearance on BOTH sides of the journals. As in.. If you think you have .030..you need to be able to get .015 on both sides, with TWO feeler gauges. hopefully when you check it with 2...you can only get a 9 on both sides?

If you just stick a single .030 in the middle, thats not how we do them. you can rock the rods a few thou "triangularly?" lol and give a falsely high reading. worth trying.