Keep in mind that the later LA manifolds have a smog pump port below the exhaust port. Depending on which head casting you're using, that might a ***** to seal. What year and model is the engine going into?
Just chop the factory air tube that goes into the manifold 3/8" long and weld that tube shut with a wire feed.
Then bolt that on with the factory bolt and the available gasket with your exhaust manifold gasket set.
Those Truck manifolds are available brand new aftermarket if you can't find good used ones. Also remove The heat riser butterfly and shaft and weld those steel sleeves shut too.
