Should not have to disconnect horn wire, (but that may depend on year of truck). I just installed a new steering gear box/mast in my 51 (and it made all the difference in the world), but I did what Forty9 said. After I got it all installed, test drove it, I saw that the steering wheel was off a little. Pulled the steering wheel, rotated a few degrees, put it back on. Now, going straight down the road, steering wheel is horizontal.
But on my 51, the horn wire did not have to be touched. It's soldered to the upper column bearing, so it's all below what you're going to be fooling with anyway.
