Ebay GT45 + 5.9 Magnum + E85 blow thru

Johnny Mac said
They're probably these. glad to see they fit! i'm looking to do a similar build in the future.

T3 T4 Turbo Exhaust Header Manifold For 66-96 GM SBC Chevy 305 350 400 | eBay

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Thanks I've actually thought of trying some of those. "Back in the seventies" I modded a set of SB Chev headers to fit my 340 Landcruiser. The port spacing is almost exact, you literally can cut off the flange and weld them back up