This is a story about building a '67 Chevy II with a modern drive-train, brakes, and steering. The body came out of a shed behind a barn in the middle of a cornfield in southwestern Virginia. It features genuine N.O.S. quarter-panels and fenders, combined with a frame and rollcage from Art Morrison. The motor is an LS1 from a '98 F-body, which came complete with two spun bearings. I got a complete replacement bottom-end from Lingenfelter Performance. The transmission is a Viper T56 six-speed mated to the LS1 using a GM bellhousing. I haven't done it yet, but I will have to replace the input shaft with a GM version since the Viper and GM input shafts are different lengths and diameters.
The rearend is a 9-inch Ford, narrowed by Art Morrison. Both front and rear suspensions are coilover-based; the front is a Mustang II-derived design with tubular A-arms, and the rear is a four-bar with Panhard bar. Baer brakes are sitting in boxes, waiting to be called on to stop the car...if it ever gets going!
Obviously, no header company makes a header specifically for this combination. That's where Headers by Ed comes in. Eddy Henneman sells header kits for oddball combinations, though they require some fabrication skills.
After I filled out his extensive questionnaire, Ed recommended a 15⁄8x36-inch equal-length header for this combination. This article outlines how I made the driver-side header.
The kit comes with mandrel-bent U-bends and J-bends, collectors, reducers (from the 3-inch collector to a 2-inch for the exhaust tubes), some straight tubing, O2 bungs, and flanges. Each flange is 1⁄2-inch thick, with about 4 inches of tubing TIG-welded in place and ground smooth, which really saves time during fabrication, since you don't have to dress these welds later when the header is complete.
The Headers by Ed kit includes an assortment of mandrel-bent U-bends and J-bends, collectors, reducers, O2 sensor bungs, cylinder-head flanges, and some straight tubing. With some fabrications skills, this pile of pieces can be turned into... | 
...A pair of custom-fit LS1 headers. The following steps outline how we got from there to here. |
These closeups of the flanges from the side and from the head mounting surface reveal their thickness as well as the smooth, perfectly ground mating welds. Shouldn't have any exhaust leaks here. Also pictured are the collector and collector flanges. | |
Design
The first step is to determine how the tubes will be routed. In this case, I wanted each of the tubes to have the same length (36 inches), so it was even more important that I spend time at the beginning before cutting up any U-bends. The basic idea is to start on the most difficult side (usually the driver's) and route the front tube as far back as possible. This provides more room to mess with the other tubes on the driver side to get them to the same length, and also makes it easier to get both collectors in the same relative location so a balance tube between them is, well, balanced.
As you can see, I've bolted the flanges with starter tubes onto the heads and inserted some pieces of wood with holes drilled in the middle. The wood pieces are functioning as adapters so that the 3⁄32-inch welding rod (acting as very flexible tubing during the design phase) will stay in place as I move it around trying different combinations. The welding rod is 36 inches long and stiff enough to make it just about right for generating curves with a 3-inch radius like the U-bends in the kit from Headers by Ed. The long wooden dowel running parallel to the flange (arrow) is simulating a steering column. It's 1 inch in diameter, which is about what common steering shafts are with U-joints.