As opposed to spending money on parabolics, then refreshing the rear springs is an easy task, and much cheaper, too!
When I replaced my back axle I soaked my original leaf springs overnight in a bath of oil. Be careful of getting any oil on the rubber bushes although poly bushes should be ok. The difference in ride quality was quite noticeable, there was far less crashiness and much more of a compliant ride quality. In fact I think I noticed more difference in mine than I did in a car fitted with parabolics.
Some advise wrapping the springs afterwards in Denso tape to stop water getting in and to stop the oil leaking out. However, others advise against it as it traps moisture. That said, I suspect a good grade of water resistant grease would protect against rust anyway.
I was sent an article by Phil McNeil on how he tackled his springs, and before reading, he categorically states, and quite rightly, he accepts no responsibility for anyone following this that hurts themselves or damages their car!
His approach was to disassemble the springs and remove the rust, paint and reassemble. If I were doing this I would use POR15 directly on the rust as my experience is that this will stop further rusting and the POR15 dries to a very hard finish.
The rear springs on my 78BGT were giving a very harsh ride, not what they should be, so I decided to investigate.
Lying on my back under the rear of the car I noticed that the springs were very rusty, not very good for springs that were less than 5 years old so I decided to take them off and clean them up.
First I jacked up the rear of the car and placed blocks under the front wheels.
Then I placed axle stands just in front of the front spring hanger with pieces of wood to spread the load. I also placed the rear wheels on blocks as I wanted to leave the wheels on because the car was inside the garage and there is very little room to get the wheels off.
With the trolley jack at hand I placed it under the middle of the spring where the u shackles attach to the springs, the reason for this is that when the 4 nuts are undone the spring will drop about 8 inches.
Having taken off the 4 nuts and lowered the jack then undo the rear hanger and the front hanger and pull away from car.
Before taking apart the springs make a note of which way the leaves are or take a photo.
Then carefully prise open the clamps around the leaves and undo the centre nut.
With the leaves separated, set to with a rotary wire brush in a drill and clean up.
Once clean apply Hammerite black paint (smooth) and leave to dry.
When dry apply copper grease between leaves and reassemble back together and insert the nylon spacers.
Fit back onto car, front hanger first then rear hanger, place trolley jack under spring and lift spring up into place, attach the 4 nylock nuts onto the U bolts and tighten up.
Repeat for other side or do the both sides at the same time but don’t get the leaves mixed up.
Lower car off stands and enjoy comfortable driving.
Rain and water will wash off any excess copper grease so don’t worry if you have used too much.