[boodlefoof]

I am going to be putting a stroked 400 into a '63 Tempest with an aftermarket front suspension crossmember and steering rack that will make clearance very tight for headers and steering linkage. As such, I have to design and fabricate my own headers and steering linkage.

I currently have the block mocked in place with a set of 6X heads on it just to get an idea of clearances. I hope to fabricate the steering linkage and headers now with this mock-up in place. However, when the engine is built (finances dictate this will happen later this year, at the earliest), it will have a set of Edelbrock heads on it with a round exhaust port.

I have found that I can mount the round port exhaust header flanges to the D-port head by using the outermost two flange bolts. I'm hoping the D-port head with the round port flange on it will serve as an acceptable mock-up to build the headers.

So the questions...

In short, will I be asking for fitment problems later when I swap heads if I fabricate the round port headers by bolting the round port exhaust flange to the D-port head? Specifically, are the spark plug angles and locations the same on the 6X head as they will be on the Edelbrock round port head? Will the flange location be different between the two heads (e.g., the angle that the flange points off of the engine, or its height/lateral location)?

I want to get this part of the project done, but don't want to fab the headers and then have them interfere with the plugs, or run into the steering linkage or frame when I have the round port heads on there.

Any thoughts are much appreciated.