I've recently converted my 305 from an electric to vacuum advance distributor setup. However, the 2-port thermal vacuum switch that was already on the manifold had a bad vacuum leak. Ordered in a replacement from O'reilleys only to find out it was open cold instead of hot and also broke into pieces while I was installing it. What I need to know is what the color codes mean for the switches and what part number I need to order to replace it. In addition, what is the purpose of the 'Ignition ported' switches with the small hole in the base VS the standard kind that don't have this hole, and which one do I need? Is the hole to give the engine more air during an overheat condition? I have no other engine to reference or get parts off of to determine which switch I need and don't want to return anything if I order from an online seller and get the wrong part. The original switch has this 'ignition port' and all emissions equipment has been removed from the engine.