My 528 Cummins assembled engine had several problems the biggest being the finish on the cyl walls was too rough and wore the rings square. These engine were not run, just spun to test for oil pressure, etc. Eventually Ray Barton rebuilt my enigine on Chryslers tab, it's been right ever since.

Yes the retainers are slightly smaller than the springs this is not a problem. The factory valve job is also questionable.

The head gaskets were also rubbing several pushrods.