I can't speak for the kits but all of the kits use the Buna-N o-rings. You could buy any of the kits and also buy Viton 75 o-rings for the 3 float needle seats . The brass needle seats have an o-ring to seal the seat to the carb body. A Buna N o-ring in that position will be exposed to the fuel and cause the o-ring to shrink. Flooding could occur as fuel escapes around the needle seat and in to the carb bowl, then flood the engine eventually.
I like the idea of changing out all of the o-rings to the Viton but in reality only the o-ring on the seat is an issue. The o-ring on the carb drain screw on the carb bowl only seals the drain screw to the carb bowl when the screw is open. Once the screw is closed that pathway for the fuel no longer exists.
The o-rings on the idle air jets don't see fuel either so Buna N is fine for them as well.
As for the carb kits, unless they come with new Stock jets you're wasting your money. The only real thing you need to overhaul the carbs is the carb bowl gasket and the Viton 75 o-ring for the float needle seat.
and of course, one of Scotch's flushing tools These are the nastiest carbs to clear circuits on that I've ever worked on
Scotch to verify??