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If you don't get any answers here, you might try the inline 6 section as many of them (us) are running that header.
I have that header in my '79, but it's a 4x2, so I can't be of much help. However, while I love having it, it was a pain to install. I had to reroute the transmission lines as well as one of the brake lines. I had to remove one of the motor mounts and hold the engine up with my hoist while sliding the header into place, and then bolt the motor back up. You also can't remove the starter once the header is in place, so I switched to a mini-starter. I would think that at least those issues would apply in your case, but I imagine there is some cross-member or drivetrain issue with 4x4's that prevent them from being a universal application, otherwise the application list would probably say so. However I can't say for sure.
I had some set of headers on my truck when I bought it, and when I converted it to 4wd, they aimed right at the crossmember. The shop had to really work to get the pipe to clear.
I don't know what brand they were, but that's about the only thing I can think of that would make them not fit.