So I will have limb lengthening surgery sometime next year. I will not mention which doctor I will be doing this with as I don't want any negative comments to change my mind on this. (No matter which doctor I say, someone will say something bad).

I want to gain 3 inches (7.5cm).

Can people recommend which type I should do?

Things to consider: I don't mind how long it takes. I can leave life behind for a year..no problem. So I won't be needing to rush it by trying to gain 1mm a day and instead will do .66mm a day.

What else is recommended if I don't mind spending a whole year.

My current weight is 55kg. Which is good I think because you should be under 60kg?
Also I am 5'4 with a slim, non muscular build.