A GMC 270 will bore safely to 3.9375 for 292 cid. You will not want to exceed that number on the street, especially with a supercharger! The GMC block is 1.5 inches longer than your 235. Patrick Dykes sells "Venolia" pistons and other parts for the 270, and cams ground by Donnie Johansen. Tom Langdon sells reproduced "Nicson" cast iron headers and used intake manifolds. Memphis Equipment sells NOS parts for military 302s, many of which will fit your 270.
With a four-inch stroke, you are well advised to keep the rpm to a maximum of 5,000 on the street. Torque, not horsepower, is the great strength of these engines, and torsional vibration is their great enemy. A Fluidamper is an excellent investment. Take it easy on the blower boost. If the engine is breathing well, five pounds will likely be more than enough. Nothing shortens engine life more quickly than the notion that "if some's good, more's better."
God's Peace to you.
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Inliner #1450
