Timing Chain

I was doing some reading a little bit ago on the 318's and it suggested that a "true " double roller timing chain be used. I have to admit that I'm confused here as I've always thought that the double roller timing chain were "true " double rollers. Also it said to use a cam as close to the 340 cam as possible, does this include all of the specs of the cam or just the lift and duration at 0.050"? Thanks everyone for your patience. I'm working on asking my questions in a different manner rather than making it sound like I've had some experience with the topic.