Hi there,
I am sorry to be negative here, but automatic chokes are terrible!! Pain in the a*** to set up and usually cause the engine to over rev or stall when its cold. I am sick of my auto choke and every auto choke I have ever had!! So obviously my advice is to keep the manual choke and decide for yourself how much to give it. Will give you more power that way most probably and also save you on fuel too. Unless you have better luck setting it up than I have over the last 7 years!
If you are reeeally sure you want to fit an auto choke though; then a weber specialist will probably have a kit you can fit, or fit another weber with an auto choke fitted already. It will have to be plumbed into your coolant system so it activates as the engine warms up.
Hope that helps!
Si