^ your cars not OS boe get over it, those turbo manifolds aren't really any use for quads are they.
Make it from alloy, so much easier to port match it afterwards and stainless is way to heavy. Chopping the original manifold is going to be an abortion make up a flange for the head and 4 flanges for the throttles and get some cunt to weld some pipe in between at the length/angle you want. Then drill holes and weld on injector bosses also weld up some mounting points to bolt the fuel rail down get a after market computer and tune