I want to use these manifolds in my Duster project and I need suggestions on how to plug the air ports. They are off a 75 360 Roadrunner. I know they are not A-Body manifolds, but others have used them on A's with minor grinding here and there. My 74 318 has stock 74 heads with a 1.88/1.6 valve job. They are ported and gently decked, and I am looking for decent flow through the manifolds. Any suggestions on plugging the air ports are welcome.