Here's a link to a site which has engine/frame details.
http://www.ozebook.com/compendium/suzi/ ... engnos.htm" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;
So yours appears to originally be a 1977 B model - now with a 1975 M engine. This used to happen a lot if someone destroyed their engine and just put a fresh one in (from a crashed bike instead of repairing the original one). The tank paint appears to be an A 1976 model though, so there's a mix up somewhere.
The carbs are a different matter as they are off either a J 1972 or K 1973 model. There will be a separate choke lever on the handlebars for these which operates via a one into three cable system and the throttle operates by a one into four system (4th cable goes to the oil pump). The carbs you should be linked together and have a push/pull throttle and a lever on the left carb for choke. If you pm me your email address, I'll send an early service manual which has carb details and other stuff that was common on later models anyway. The tickover screw on the left carb should be on the left of the carb, not the right like the centre and right carbs.
This link
http://www.suzukicycles.org/GT-series/index.html" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false; gives more details and this link
http://www.oldjapanesebikes.com/mraxl_G ... /index.php" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false; tells the history and differences of the models. I suggest you do some reading!
The early carbs will work on later engines as it looks like you have 'iron bore' barrels, but you'll have to keep an eye on mixtures when you get running. Sometimes the chokes stick, or the choke cable can break to one carb and that will cause bad starting/not running on one cylinder. Also try removing the plug cap from the HT lead and cutting 5mm off the lead, then replacing the plug cap. The leads deteriorate over time.
This link
http://www.alpha-sports.com/suzuki_parts.htm" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false; gives parts details.
Find the year, then model, then which part of the bike you need to look at.
Think of how stupid the average person is, then realise that half of them are more stupid than that.