I suggest a set of Fenton cast iron headders, with a set of thrush magnum glasspacks in 2" 31" long. It has to be a 235 because I don't think chevy even made a 285, they did make a 261 but that came out after 1956 I belive. The stock intake manifold will not work I do not belive, you will need somthing like an offenhauser intake, I'm gonna get the 3 carb but there are 2 carb 1's. I put a glasspack on my car with a new temp exzaust ( so my neighbors/ neighborhood/ town woulden't complain because of the racket ( compleat open exzaust ( just a small portion of the first exzaust tube remained ). ( I live way out in the sticks and I ), with the 1 glasspack, it sounds like a v8 at crusing speeds and at idle somewhat, I can't wait to get the duals on it with the smitthys mufflers ( glasspacks that were popular in the 50's ( still produced ) with the fenton cast iron headders. www.speedwaymotors.com has all the parts I mentioned.