[big gear head]

I had this problem several years ago when working on a '68 Camaro with a 396. I put a high volume electric pump on it with a bypass regulator. I thought that the #8 supply line and the #6 return line would work fine, but it didn't. Same problem that you are having. I couldn't get the pressure low enough. I had to install a #8 return line and then everything worked great.