Slant 6 headers & 4bl intake manifold

I can't help with parts, but I can give this a bump and offer some advice. Hooker still makes a 6 into 2 long primary style header that is available from Summit. The drawback to the Hookers is that they have 5/16" flanges instead of the needed 1/2" flange. 3/16" spacers are included in the hardware kit to allow the exhaust and intake to mate up, but they are a royal PITA to install and properly torque. The Hookers also have provisions for exhaust heat to the intake manifold. The only other viable alternative from an availability stand point, are the Dutras. You have two options with them. You can buy front and rear manifolds, or you can send him your old exhaust manifold which he will modify for use on the rear 3 cylinders for a fee, and sell you the front manifold that he manufactures. If you buy both manifolds you will not have intake heat which may cause cold start and/or run issues depending on your climate. Buying the front manifold and having your old one modified will retain intake heat for winter use if needed. The Dutras also have the advantage of being made of cast iron so you don't need to worry about them rusting out and needing replacement. Me, I'm taking the third option and making my own. Hope this helps.