Hello folks. I'm looking for advice on what changes to AMAL carbs provide the best tune after replacing stock exhaust. The bike is a 69 a75 (20 thousand original miles) with original 27mm 626 amals and stock internals and jetting. Im replacing the rayguns with a Big D 3 into 1 header(purchased new 1973). The engine is stock with good compression and oil pressure. The ignition is Boyer digital power. I suspect most of the changes should be in mid range to top end likely requiring larger main jets,perhaps a smaller # slide cutaway and possibly raising the needle position. I don't anticipate changes to the needle or pilot jets or for that matter the float levels. Im sure there are quite a few members familiar with this header who in the past have installed it (or similar units) and arrived by trial and error at the right combination. Im asking because all these AMAL bits and pieces are quite pricey (read exorbitant) and here in Canada, at least in British Columbia, no longer readily available at your local brit bike shop(there aren't any) so Id really appreciate any help getting to that sweet setup faster with less expense and without a handful of parts that prove useless.