will a drop spindle from a 74+ fit on a 73

cool, will give it a try later this summer

I have not done this swap.  Based on my measurements, the 73 and 74  tie rod ends are the same.  Rockauto.com also shows the same part number for both.  The 71-72 are the ones with smaller tie rod ends.  This assumes no end of year carry overs.
 
Note that 74  spindles (including the drop spindles) are about 7/8" taller measured ball joint to ball joint.  If this is the only change, I believe this would increase camber gain during bump.  I measured the vertical distance from the lower ball joint hole to the spindle centerline with the following results: 72~2.5", 79~1.4", drop~3.4".  So the 2" drop spindles will lower the 71-73 cars by about 7/8" based on this.  Again this is based on component measurements and not on a final installation.