I searched the site and see some discussion regarding freeze plugs, brass or rubber etc. However, I have a 73 CJ5 with AMC 304. After removing the exhaust manifold I see that 2 of my freeze plugs, are "weeping" or leaking a little. I was thinking now is the time to replace them. When searching the American Motor Parts site I see that there are a couple of different sizes, 1in, 1.5in and 2in. Which on is the correct size metal plug for my 73 304?