That plastic ball is basically a 'safety' catch if the rubber mount fully fails. As long as the rubber section isn't falling apart or visually cracked, the mount is probably fine. There is definitely supposed to be some clearance there.
Here's about the best shot I have from the last day my 4Runner was 2WD:
-Charlie
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'99 4Runner SR5 Auto -
4WD swapped
'89 Camry Alltrac LE 3S-GTE 5spd
'17 Chevy Volt Premier
'16 Honda Odyssey Elite
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