The Weber is the way to go for an instant nut and bolt swap that solves a bunch of problems. We have a listing for what to look for and which trader to buy from in regards to getting the real deal. You can do bike carbs - but this is not a straight forward thing to get up and running

https://www.youtube.com/watch?v=gFunG5Ku-fI

This guys' handle is Superscan811. You can find his build thread on sigma-galant.com and it will give you a full run down on his carb install. I think that his build needs a sealed air box with an intake duct on it to alleviate the low down throttle response issue and his manifold is rough, but the bones of his set up are solid.