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What tbascom (Tully?) said. If you mean the link from the steering box and pitman arm, down to the tie-rod, then that's called the draglink.
On 4wd trucks, there is a link parallel to that one mounted between the frame and axle, called the trackbar.
Agree too that (normally) a 3" lift won't necessitate longer shafts. Even on short-wheelbase Broncos they don't need longer shafts for 3" of lift on 95% of them.
Of course, even with the same odds you could be one of the unlucky 5%!
One factor in that is rear pinion angle. If the block has a taper and they installed it backwards (thick section forward, thin to the rear) the pinion will point down more and create a mistaken need for a longer shaft, when in reality you need to raise the pinion to correct the angle.
So, is this '79 a two, or four-wheel drive? Standard cab, Super-Cab, or Crew-Cab? Not many of the latter around, but they exist. This could change the answers for the rear shaft.
Is the rear driveshaft the usual single-cardan style (one u-joint at each end) or the double-cardan style with the CV yoke at the top near the transfer case?
Those answers and maybe even a couple of pics would be great.