I am in the process of setting up a rolling chassis for my '50 styleline. I'd like to mock up the engine and exhaust soon. I've been looking at both the Fenton and Nicson manifolds available and was wondering which would be better for a mild 270 build? The Nicsons look much beefier and have 2-5/8" collectors vs. the 2" ones for the Fentons. Conventional wisdom would say that the Nissans would flow better, but realistically, I think I will be running 2" exhaust tubing at the most in order to keep up velocity. Would the larger ports of the GMC be negated by necking down to the smaller sized exhaust tubing? Any advice here on the manifolds and tubing size would be appreciated. Thanks.