Hi Jim...
I just got home from work and started reading this thread, and as I was reading, it occurred to me what the problem was, because its the exact same problem I was having with MY car and I posted that some weeks ago! Too bad I didn't see this post earlier so I could have helped, but I'm glad you found the problem.
Now, onto the issue of your NSS. Bruce is correct, try to fish out the old piece, just for your own peace of mind, but if not, don't worry, it wont be in the way.
My car is a 68 CdV, so the switches may be somewhat similar.
Look at my old post for what I had to go through. My switch also operated the vacuum switch on my parking brake release, and there is no direct replacement for it. Not wanting to pay BIG BUCKS for a used one ( I was quoted anywhere from $100.00-$300.00 ), I ordered a similar new switch through NAPA auto parts ($25.00, Electrically it was the same as 1968 Chev, Pontiac, Olds, etc) and I made my own replacement switch from the plastic part of the new switch and the metal part of the old one. On my switch, it was the black plastic part that broke.
When you go to install the new switch, if it like mine was, it will come from the manufacturer in the Neutral position and may have a shear-pin holding it in neutral until the first time you shift it. Obviously because I had to "frankenstein" my switch, I didn't have that shear-pin, but it was pretty clear from the look of the switch where neutral is.
SO...place your car in neutral (with the brake on and wheels blocked, of course!) and connect the wires, start guiding your switch into place...you'll have to finesse it a bit, and you'll feel it drop into place. Depending on how your switch mounts to the column, it will have a bit of play so that you can make finite adjustments. Snug, but not tight. This is also your switch for the back-up lights, and you want to make sure they go on when you are in 'R'. Then make sure the car starts in Park and in Neutral and the back-up lights work in Reverse. When its all adjusted, tighten it up!
Good luck!