recommendation for carbs on new motor

I'm restoring a 1976 KZ900 purchased a new built motor with a 1260 kit welded crank not what cams but I believe RC brand. Need carbs I have a set of 28mm pumpers should I step up to 29 smooth bores or 34mm flat sides? Any thoughts.

Im no engine guru and im sure the 28 pumpers will work but with a 1260 kit i would say let that motor breath and use the 29 smoothies or if you got the coin spring for a set of flatslides. I have RS34 carbs on my 1075 with street port and polish and mild cams and it rips.

Depending on what the head flows I would rum 36mm if it has a good flowing cylinder head on it.