[Mr70]

You can't tell from looking at it if it has sulfated.
What's happening to your battery is the cap air filters are clogged.This doesn't mean the battery has sulfated.It happens on some of them and is completely routine.Pull off all the caps and gently insert a tooth pick or ice pick down into the small cap air hole until it snaps out a small white semi soft plastic pourous disc filter out of each one.
Put all 5 filters in a dish and sprinkle in alot of baking soda & fill up with water.Put something on top of them to hold them down under the baking soda/water solution.They will suds up a bit but thats normal.Let em soak overnight.Pick up each one & run cold water through them on both sides until they let water flow through them.Make sure you neutralized them w/baking soda cause your gonna blow through each one on both ends until air passes through them freely.Preferably outside away from anything.
Set them on a paper towel and let air dry overnight.Wipe the inside of the caps out too with a paper towel.
Push the filters back into the bottom of each cap until you feel/hear a "click" and reinstall them on the battery.
This is common routine maintence to any WET battery per Delco's instructions back in the day.
I would also check each level of your cells while your at it,to be a within 1/4 inch from the top of each cell with a splintered popsicle stick marked off with a pencil showing 1/4"...but no more then a 1/4.
Also,use a battery hydrometer to make sure the cells are all at full power,using Distilled water only if needed.
If any cell is below 1/4 for an extended period of time,there's a very good chance it has begun to sulfate and is dieing.
I've been through 3 WET R-59's,constantly maintaining them for a total of 14 years of life out of all of them altogether,before I bought the new maintence free SR-59 last year.I know some who have gotten 7 years or more of life from a WET battery,others 3 or less but I know I'll never buy a WET battery again.

BTW-That "Danger Poison" battery terminal label is vastly gaining on the "Caution Fan" sticker and upside down Cowl Ind. rubber seal as the number one most seen incorrect item on otherwise correctly restored vehicles.That label was included to meet todays shipping codes when shipping a caustic battery in a box over the counter and was not put on the vehicle at the assembly line originally.