I find it hard to believe that the plug solution is the best that intellegent minds have come up with so far. The problem with using the plug with the tapered hole is it throws off the geometry and the plug will not be held in any better than a replacement ball joint. (If they were available). The center of pivot moved from inside the bore of the upright  to a location 1+ inches away. Why hasnt any one tried threading the bore and using one of the heavy duty MOOG threaded ball joints This is not a conventional thread type so a tap is not available. At least I couldnt find one.. I have used a rounded off threading tool on a boring bar, mounted my LCA on a face plate and used my lathe to create threads at 50% of the full depth. This helped the ball joint to start threading in square and was still plenty tight to avoid comming loose.. I had excellent results using this method... These ball joints were originally a chrysler part and come in a wide variety of sizes. Now they are as common as dirt in NASCAR. Phantom jock is right about heating the aluminum to release the steel ball joint with out galling.  This works surprizingly well due to the difference in expansion rates.  Does any one know what alloy the vette uprights are made of or if they will anneal by heating them? The last thing you would want to do is soften the critical area around the ball joint. Right?

That worked, so here's the other angles.