Vahid if you find out about a kit to convert to adjustable needles I hope your will post it here. I would be interested too. I think the later Strombergs could be adjusted with a special allen type wrench to reach down into the bottom of the damper oil reservoir to adjust the needle. Seems to me it would take at least a different carb top and piston/needle assembly to do this but I don't have a Series lll manual to see if it might show how the adjustable needle type works.
David Barnes
68 E-Type FHC