google Peter Demar and read his articles. probably one of the foremost people in the battery restoration business. with distilled water, catalyst caps and a specific charge regimen he can bring most back to 100% capacity. on VRLAs the lugs cant be pushed out too far.
armed with info from his articles and reckless abandon for free dead car batteries, i have had about a 7 in 10 success rate restoring 12vdc Lead Acid cells by opening the caps, filling with distilled water to about 3/8" below the tops of the vent slits, then hitting them on 200amp start mode from a sears battery charger. this is around 15vdc. i do this till all cells are "boiling" more or less equally, say 2-8 minutes in a vented area to burn off whatever sulfur i can. then i close them up and leave them on 2amp slow charge for a half day or so. if the battery isnt badly bulged and hasnt sat discharged for very long, it will almost always come back. some have come back 2 or 3 times.
this has saved me hundreds in battery replacement cost to be honest. i have a bench full of good batteries that i pop a float charger around on every other day whenever i walk by. they were all throw aways.