RC,
I agree with Pintosopher. Bolting on headers doesn't always give you power, nor will bolting on a 4bbl. The root problem with a Cologne V6 in the US is that they have little compression. If you look up the numbers from a euro Cologne V6, you will find that they have 50% more HP in some cases (make sure you are comparing like figures, ie. net to net or gross to gross). The reason for this is not a holley 4 bbl or headers, it is compression, cam and timing. A bigger carb will burn more fuel but not give you a proportional gain in HP. Power is all about efficiency. The more efficiently an engine runs, the more HP is produced. Here is an example.
I have two Fiat Stradas. They are identical, including engine type, 1500CC 138A SOHC I4.
One is a US model with US cam, compression (7.1:1), carb (weber 28 dmtr).
I also imported one from Italy with all the euro engine bits: cam, compression (10.2:1), carb (weber 30/32). The both have the same intakes and exhaust manifolds, the same blocks and cranks, both have cats and stock exhaust.
Here are the numbers. Federal Spec Strada: 60 HP, 54 LBFT Torque.
Euro Spec Strada: 110 HP, 101 LBFT Torque.
Those numbers are astounding (Mind you, Fiat engines are more akin to the Cologne 2.8 than anything else Ford has made. Ford used Lancia's V4 to build the Cologne V4 which turned into the V6. It is the Italians that pioneered the V4 & V6 so the cologne had a lot of distinctly European traits).
If I bolted a header to the federal car, there would be no significant delta. On the Euro one, it would go up about 15 %. The reason for this increase is that the car needs to breathe more. The federal one does not because it has no compression, just like the Federal Cologne motor.
If you want HP, you need to do REAL engine work. Change the pistons, cam and timing. You will not need a 4bbl. Those are misconceptions of the V8 community. A holley 350 is perfect. Once you do that, THEN you can consider headers. Until then, you are burning fuel and money to get less HP. Trust me, been there, done that.
Go on to British Capri and Taunus forums and see what they are doing. Simple as that.
I know that is not the simple or cheap news you wanted to hear but it’s the thermodynamic truth.