I used the manifolds in the photos below on my 82 C10 with GM Vortec heads. They are sold as Dorman and other brand names.
I had to raise the tops of the exhaust ports a little to match the raised ports on Vortec heads. You may also need to do this on other manifolds and headers, as well as choosing your gaskets well. You can see in the second photo below how some exhaust gaskets obstruct the top 1/8"-3/16" of the Vortec exhaust port. That's the last thing you want to do, because exhaust gases are the most intense at the top of the port.
The last photo shows the gaskets I used. I can't remember what they are for, maybe Fel Pro gaskets for 97-up 5.7 liter 1500 trucks. Oval shaped gaskets might work, too, like Hedman #27520. Fortunately, the heads have a wide gasket surface around the ports.
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