Hi I'm just about to start up the Pontiac but I have to drill out the heads for NPT to An male fitting. My question is, what size line should I use. I want to run two lines from the tops of the heads to the top tank on the radiator. I bought 12an but now they look a little big. I was thinking I could put in a sleeve to increase the pressure, but also how they look is important. Maybe 10an would look cooler. Plus I did a search and I couldn't really find what i was looking for. Anyone done this? Thanks, oh incidentally, 331 Hemi, stockish hydraulic cam, 8 to one around ten pounds of boost. Nothing special really but it's my first blower motor. It wouldn't let me load photos of the car for some reason, anyway thanks.