Well there's lots of options out there. People go with those because they're the best known. I went with a set from Cushman Motorsports because I'd heard great things about them and also because I was able to get them for $600 on a Black Friday sale a few years back. Lunati also makes several sets of cams for the 4.6 3V, and I know there are others as well. NSR cams give about the same results regardless of brand, so it comes down to what sound you want and what kind of deal you can find.