You dont use vac advance with twin carbs. Ideally get the dissy modified to run full mechanical advance and curved to suit your cam.
As for tuning the Dellortos ... the best advice you will get is take it to someone who knows what they are doing and get it set up correctly. Otherwise you will just waste money buying jets and emulsion tubes that you will most likely end up not using, and they arent cheap!
Unless you have a gas analyser and preferably a dyno you are unlikely to get them close to right.
Been there done that