Need new manifold.........asking for help please
Unless you want to buy a used manifold (which is not a bad idea, at all), I'd reccomend the "Crosswind" Air Gap-style maniflod by Professional Products. It's a Chinese knockoff of an Edelbrock Air Gap 180-degree (dual-plane) manifold, but has slightly smaller ports, which could be good for your 318.
It's a little over $150.00, while the Edelbrock manifold is roughly $100.00 more.
I have had a Crosswind on my car for a couple of years with no issues of any kind.
If it's worth it to you to "buy American", the Edelbrock is a great manifold!!!
Edelbrock wasn't selling any Magnum manifolds yet, when I bought my Chinese manifold, and I needed a manifold so I went ahead and bought it and I have to say, it's been trouble-free. Of course, a manifold doesn't have any moving parts (hopefully!), so that's not surprising... 8)
Good luck!
Bill, in Conway, Arkansas