You need to find out how long the primarys should be for your engine first and go from there. How big the motor is determines size of tubing. and collector
Making headers from pictures and measurments and going home to bolt on just is not going to happin, there are alot of bends and obstacals that come into play. As well as tube diam and lenghts. I would suggest a mock up car build then make the headers to fit the mock up. Here is a top veiw of mine. they clear the foward rollbars by 1/16th. These are speedway headers off a 55 or 57 chevy, dont remember.
I used a bare block and heads. Mounted clutch linkages and any parts that come close,roll cage, set motor mounts and go from there. Use the same heads and block configuration as there are tall decks and tall port heads. You need to be accurate as possible. Hope this helps
Those measurements are exactly what they look like. A is how far the outer most part of the header is from the heads. B is the height of the header from the highest point to the lowest C is how long they are from the front of the first tube to the back of the collector. We (Patriot) make those headers. They are for fat fendered cars - no reason to try and adapt those when we make Nova Fenderwells as well.
Watch all 6 parts. They show you how to do a PVC mock up. Build that and the fixture,then take em' to your school to build. http://www.youtube.com/watch?v=j9knDsi-td8 Brandon