Interesting re the difference between the pattern part spring and the OEM spring! Of course, the actual relief pressure might be similar due to the compression of the longer, thinner spring vs the shorter, thicker OEM spring. But the OEM spring does look more "right" for the application.
Can't think of a good way to actually measure any relief pressure difference between the springs.
Maybe I'll disassemble the filter and put the original bolt back in! I'll ponder about that...