I haven't done a complete non-a/c to factory a/c swap but both my '71 Sweptline and my wife's '79 LRE were factory a/c trucks with ALL of the underwood components missing. For each one, I found a junkyard donor for brackets and pulleys from a later model with the Sanden-style rotary compressor, ordered all of the new components from Rock Auto or Amazon, and bolted it together. The '79 was pretty easy for lines as I just got parts for an '88. For the '71, I ordered the correct lines for both a '71 AND a, '88 and had the local a/c shop cut and splice them where I'd marked. Both were getting a cam and manifold change at the same time, so there was minimal additional work.