Refurb your old carbs, that's what they came with and always the best option as many others will agree I'm sure.
Completely depends what you want out of your bus. A Porsche engine will go in (it's not quite as simple as the 4 bolts the bloke down the pub will tell you though).
Not if they are set up properly, if not I suppose anythings better. Find someone who knows how to set them.
Solex carbs are good. They are probably original and need refurbing and tuning. I got a 'new' refurbed solex for my 1600 from Kevin at Riverhaus. Maybe he can refurb yours if you are not doing it yourself.
