After giving up trying to install a 20lb spring from the parts kit, I ordered a 14lb spring that Wolff says is what was in the gun at manufacture. However, when I install it, the guide rod protrudes about 3/8" from the muzzle end of the slide. I also have an early W. German 220 made in '89, and the barrels won't interchange. That model easily takes the current 20lb green spring. Any idea what is wrong here? By the way the guide rods are identical in these two models.

Solution? Switched the guide rods between the '89 220 and the '78 Browning 220, and problem solved. At least they both work now. What just happened? Never had them apart together before, so I couldn't have mixed up the parts. Or could I have?

I have had the wide end of the guide rod somehow land on the takedown lever a few times. Protruding as you have described. Sometimes rotating the rod will allow it to center into the proper position.

This, assuming that both your BDA & '89 are in 45 ACP.