Replacing fixed needles with Adjustable on series 2

I am about to embark on a carburetor rebuild project on my 69 Series two with original Stromberg. I have read all the postings and found them quite useful. Bought the kits from TerryÔÇÖs and will get on it in a couple of weeks when I am back from an overseas trip. A local mechanic told me about the conversion of the needles from fixed to adjustable and said there is a kit for it. I have not found it on TerryÔÇÖs or XKS. Any comments on whether I should do it and where I could get the kit from? Also, should I get the Haynes carburetor manual? I already have Haynes Owners Workshop Manual and Jaguar Service Manual.