The tube on the #1 carb does not connect to anything, leave it the way it is. The right angle 10mm fitting (#50) is used for the diaphram vents for carbs 1 and 2 and there is another for carbs 3 and 4. Do not connect them to anything if you are using the stock airbox. You would have to connect them only if you were using and aftermarket "ram" type box for proper pressurization of the diaphram chambers. You would then route them into the box for that purpose.
On the same note my friend and I were taking apart my carbs about 2 weeks ago... I had the same question because I'm putting my bike back together. I have 4 vent lines that I have to hook up. 2 go to the right angles on the carbs I know ( I gues part #49 tthat's between the carbs) and now I have 2 more hoses left. I know 1 has to go to gas tank. Where does the other one go? I forgot and I'm excluding the one that goes to the airbox because I know where it goes. I may post pictures later.