One person somehow relocated his steering box an inch and a half over, and then was able to clear headers. He said he "shimmed" it over, which didn't make any sense to me. I asked for more details or pictures and got no response.
You're probably going to have to invent something and relocate it over. That guy heated his firewall cherry red and then moved the steering shaft over...which seemed like kind of a dumb way to do it. Flaming river sells U-joints for just that purpose, and if you relocate the steering box, all you have to do is u-joint the steering shaft.
You could conceivably mount the V8 so that it's not directly on the centerline of the truck. You've got to weld the motor mounts on it anyway, so why not shift the motor over an inch or two? You'd have to do the same with the transmission, and the driveshaft would have u-joints to correct the slight shift over to the diff...no big deal there. But I personally think it would be simpler to shift the steering box over than it would be to relocate the drivetrain over.
And GM's done that with other drivetrains. The 1963 through 1982 Corvette had the centerline of the drivetrain shifted slightly on the passenger side...probably to clear the steering box mounted on the framerail on those cars too. Also helps to counter-balance driver's weight.
