The first thing is to get a baseline and that's easy. The large nuts on the bottom of the carbs, the ones restrained by the spring, adjust the height of the main jet in relation to the tapered needle. Turn the nuts all the way up, and then back them down two full turns (12 "flats" in SU lingo). The throttle stop screws, that act on the bellcranks are set next. Back them out until they no longer contact the stops, and then advance them until they just touch the bellcrank and then a further 3/4 turn. Be sure the screws for the choke lever fast idle are backed out and do not hold the throttles open at all.
Warm up the engine, and set idle speed by turning each of the idle speed screws equally and the balance will be close. The mixture check is a bit tougher to do, but if you turn the nuts an equal amount either up or down a few flats at a time, you can find the best idle quality, and that will be close enough too.
E-mail me directly Jack for more advice at www.sucarburetors.com