Very common with the 60 amp alternators.
Look to the TM's and verify that the brackets and mounts are correct. Some have a thick washer type shim at the back ear that fall to the ground... never to be found. Then one puts it all back together unaware, pinching (preloading) the ears and soon after SNAP goes the ears.
DO NOT take up excessive play between the ears if one notices a gap of more a few thousandths. Older style cradle is aluminium uses shim, has bolt front, one rear. Note to PoPeYe... easy to strip out helicoils too.
Newer cradle is cast steel with a thru hole and long bolt. Dimensions front to rear wider. NO thick shim needed. I have slipped in a thin stainless washer to zero out any play / gap, but that just me.
UPDATE..........
There are a couple of brackets mods to fix and support these 60 Amp alternators from the exhaust manifold to the later engine block mount.
There's a lot of harmonic loading action between the engine and the phases of the alternator under load, not to mention the belt slapping. Always check ALL the bolts in this area during PM's. Power steering, alternator and NOT just the easy ones seen.
That's the third one I have seen this year. A 4 cent washer takes out a 400 + dollar alternator. I have saved a few by TIG welding with proper preparation.
Not a JB Weld job, CAMO
Added note for the 60 Amp boys.... If the alternator when running is bouncing around as in doesn't appear to be attached to to the engine... TIME to check. Not to be funny as I am, but easy to run like this way and figure must be normal, till it really lets loose. just saying.
Looked back at your pictures. You have the old lower cradle. TM time.