It's all about the bounce.
February 2nd 2020
After speaking to a couple of people on the owner's club forum, it appears that my seven leaf springs were an original fitment on early Morris Minor saloons. The leaves are slightly thinner than on the later Travellers. This means that the modern replacement would indeed be the new five leaf springs which should give an equivalent stiffness to the original ones. That's good news!
The set of pullers I ordered arrived the next day so I was able to break the taper fit and remove the old drop links from the shock absorbers. The drop links appear to be in quite a poor state so rather than buy new bushes for them and attempt to clean them up I may as well replace them for new units which are fairly inexpensive and come complete with new bushes.
Once the old drop links had been removed, I filled a plastic tub with white spirit and used that to clean up and degrease the outside of the shock absorber housings.
Once they were nice and clean it was time to open them up and remove the old oil. I have no idea when they were serviced last so I was interested to see what sort of condition they were in. Rather than using the small drain and refilling ports I decided to just remove the whole top in order to give me better access, so I removed the six screws and prised off the lid. Fortunately the old gaskets seem to be in very good condition so I will be reusing them rather than making new ones.
Once the top had been removed I poured out the old oil which seemed to contain a fine metallic residue which was a little bit concerning. The shocks still appear to function well so let's hope that an oil refresh will give them a new lease of life.
I pumped the lever a few times to push the old oil out of the valve at the base of the shock before filling it with white spirit. I then pumped the lever a few more times to allow the spirit to flush out the last remnants of old oil before refilling it with fresh SAE20.
After refilling and pumping the new oil through the valves, I cleaned up the gaskets and applied a smear of sealant to all faces before tightening down the lid. I repeated the same procedure for the other shock absorber and set them aside ready to be refitted along with my new springs.