IDK (but I suppect) if the GMC adjuster ball & pushrod cup are the same as stovebolt 235/261, but those are 11/32" - not a common size.
A 3/8" ball will not fully seat in the cup, and burn the edges, then collapse it (as described). A 5/16" ball will bottom in the cup, but make only partial contact, wear and overheat very quickly.
I like to lap them in myself, but if the sizes are correct and quality is good it may not be necessary (the factory didn't). If you do, clean-clean-clean to remove all compound!
Smith is great, the 2 other premiere pushrod mfg. are Trend and Manton.
E-mail photos to me at jdiamond@optonline.net and I'll put them on my site.
