Pulled the hood ornament. Looking at the manual, the old epoxied POS, and the (partial) new star I now see what the huge spring to the bottom of the grille is about: the locking collar is missing (on both ornament assemblies!) and the heavy spring is what's holding the whole mess in. The old assembly had its heavier (of two) springs moved from the inside of the spring retainer cup to the outside of it (below), and the inner spring was extended and had a cotter pin through it to pin the outer spring in place. (The relocated spring is what normally puts tension on the star itself so that it stays wherever it's moved to in its socket, but its lack wasn't felt because the socket was epoxied together, presumably as part of holding on a snapped-off star.) Then the whole mess was spring-loaded down into the grille's hole by the long heavy spring. Without the locking collar what else can you do? I ended up just moving the old outer spring to the same place on the new (resulting in two outer springs, one inside the retaining cup and one outside) and used a piece of framing nail to pin it in place through the inner spring's hook as before. Then the whole mess was loaded into the grille's hole and tied down with the long spring, just as before.
Highly inelegant, but functional. And it looks just fine from outside. If someday a retaining clip turned up it could easily be made right as no harm has been done to anything, so that's OK, but it seems just fine to me as it is. Done! Have I said that lately? Thanks to Kevin, for Erik the half-a-star! Now I just need to wait for the weather to clear enough to wash the car again and take the pictures. Then it goes up for sale. -- Jim