You need the 1/2" spacer to allow the throttle arm to clear the front manifold runner as you know. Hank told you right about the velocity. Run a 4 hole spacer and use a 4 hole gasket on each side of it. The Offy intake has a 4 hole adapter as part of it and the spacer and gaskets are a direct bolt on with no other work to align things. Keeping the 4 throttle holes separated will give you the sharpest throttle response and also make tuning the carb much easier for you.
