Mid Mod Guy

After lots of background processing and thought, I figured out why my part was not fitting on my Avanti for the backup lights. There’s a small metal threaded reducer that is situated between the backup light switch and the master cylinder. It's a larger diameter on one end and a smaller diameter on the other end. When I took off the old switch, this part was still threaded onto the old switch, and so the new switch didn't fit into the master cylinder correctly. Once I realized this, I unscrewed it from the old switch and then re-screwed into the new switch and now it fit perfectly and the lights work. Yay! Here is a photo with the old switch still in place, in case it helps someone else who encounters this situation.

The brake lights no longer work on my 63 Avanti. I checked the fuse, it looked fine but I replaced it with a new one. That did not solve the problem. So I ordered a brake light switch and went to install it and discovered that the threaded part is too small in diameter and does not fit or match the old part. I checked a couple different sources and they all give me the same part numbers and the same part as the one I already have in my hand. What’s going on? Is it possible? I have a non-standard master cylinder? I don’t think so. Here’s the new part that I have that does not fit.