Until you put some mileage on the vehicle and you can get a look at the condition and color of the spark plug insulators, tinkering with jet sizes is premature. Running a 216 carb on a 235 will make the mixture run rich, even with a normal-sized main jet. Plugs running the right mixture will be somewhere between light tan and chocolate brown, Bright white is too lean- - - -sooty black is too rich. The main jet doesn't begin to affect the fuel mixture until the engine is WAY above idle speed. Idle mixture is controlled by the adjusting screw near the manifold flange. I like to adjust the idle mixture for the best vacuum reading at the main vacuum port (wiper hose) for any particular idle speed, and then go approximately 1/8 turn rich (CCW) from there. Richening the mixture slightly after finding the best vacuum reading helps smooth the transition from idle to part-throttle operation.
Jerry
