Edelbrock 1406 whistling

You do not need or want to use the spread bore adapter. They are made to bolt a spread bore on a stock 4 hole 4150 intake. or bolt a 4150 on a stock thermoquad intake. they are pretty thick and not nessasary in your application. Like I said I will see what I have and you may have it for shipping cost. Or just get a 4150 base spacer. 1/4 inch thick aluminum is all you need gasket on each side. or a steel 3/32 thick. It will be a square opening. or 4 holes the same size. Steve