Jim, I updated my '65 Pickup drums to the 1972 discs. It was only a C10 but I think the same method will work. I kept the original arms and changed the ball joints and all of the steering linkages. The idler arm was the worst as we had to re-drill the chassis to get it to mount. I was told now that the easier way to do it would have been to undo the whole cross member on the '73 - '87 truck (8 bolts I believe) and then bolt it back into the earlier truck. One thing I remember hearing was that whatever year spindles you use, you have to use the same year ball joint. Take the power brake booster, brake proportioning valve and the power steering box off of the later truck as well. The junkyard hunt should work good for you.
