Well,
Someone has to be the Guinea (Gin-Wa) pig, so I decided to try the new World Products intake for rectangle ports and the 4150 carb to use on my 498.
Price is decent through Sallee Chev, and who knows....maybe it's the cat's meow. I'll never know, cause I'm not going to buy one of all the other guys manifolds to compare too.
Ron

Let us know how it runs, Ron. I too bought a new manifold this week. After some research I decided to try a Dart single plane oval to rectangle port manifold on my car. CNC ported and professionally blended. So far I haven't been able to bolt it on the car. First problem was the flange was so think it wouldn't clear the valve cover lip on my Canfield heads. No problem. Measured and marked it; took it to the local machinist to have .125 removed from the outside flange on both sides. Picked it up this evening and set it on the engine. It now clears the ridge on the heads but the intake bolts don't line up with the heads when the gaskets are in place. Removed the gaskets and the bolts lined up fine. Gaskets are .030 thick so it's back to the machine shop to have the manifold cut down .030. I sure hope my engine likes this intake. Ain't this a fun hobby?

It is a fun hobby! And there is nearly always a surprise right around the corner when doing engine projects.
Good luck with that manifold!
Let us know how it works compared to what you are replacing.
Ron