Long story short, I rebuilt the engine in a 2008 Acadia. About 200 miles after it ran again, it spun a rod bearing. I still haven't figured out why. No oil pressure gauge to know for sure, but I didn't get a low oil warning until after it spun. If anyone knows what would cause a spun rod bearing on a fresh rebuild, please let me know. Oil level was perfect. Bearing clearances were plastigauged, well within spec. Timing and all 4 cams look good, not damaged by low oil pressure.