I just purchased a new Edelbrock 1406 to replace the Holley 1850-4. I mounted the 1406 and the linkage for the secondaries hits my valve covers, which are the FORD SVO tall valve covers for roller rockers. I figured I would install a 1/2" carb spacer to alleviate this problem. My question is, both carbs are square bore but the butterflies on the Edelbrock don't match the 4 ports on my Holley Street Dominator intake (they aren't in a perfect square like the Holley). Is there a certain spacer I should use, or is this conversion not going to work? I don't want to just use an open carb spacer as I don't think it would flow correctly. I'm not sure a taller spacer would work because of the small amount of clearance I have. I can't be the only person that has come across these issues with mounting an Edelbrock. Does anyone know what I need to do in this situation? Any help is appreciated.