If you are considering building a manifold without a plenum, I believe you will have MAJOR problems using YH's as they are nowhere near large enough for this type manifold on a Chevy 235.
I would highly suggest either building a manifold with a plenum, or why not pick up a 53-54 Corvette unit to start.
If you really want to build the manifold without the plenum, consider using 3 large 2-barrel carbs instead of the 3 single-barrel YH's.
Choking will depend on the type of configuration. For a no-plenum set-up, you cannot run a primary/secondary set-up; all carburetors must work all the time. Using this type setup, if you need a choke on one, then you need a choke on all. If you don't need a choke, then you can have no choke or chokes on any or all. If you have a manifold with a plenum, then you can set the carbs up either as a primary/secondary or 3 primary. If you use the primary/secondary, then a choke, if needed, would be used on the center carb only.
If you do the manifold without the plenum, I have no clue as to where to begin jetting. I really don't think it will matter if you try to use the YH's without the plenum.
Jon.
