I had a near perfect 57 tach-drive distributor on my 55 Tbird. I had no idea when I inherited the car, and I don't think my dad (2nd owner) knew either. I didn't discover it until I went to replace the distributor cap with a new 55 distributor cap; the 55 cap is smaller. That's when I learned that the original 55 Teapot carburetor /w divorced choke was not compatible with the 57 distributor. The car seemed to run fine, no problem idling or cruising around town or on the highway, but as soon as I put my foot in it, it would miss, and the Fordomatic wouldn't automatically downshift. That's when I contacted Gil Baumgartner (CTCI Gil's Garage) and asked for his advice. His first question was, "What do you want to do with the car?", to which I replied, "Drive it." He then recommended that I keep the 57 distributor and replace the Teapot with a modern carburetor; I did. Rather than getting an adapter for the 55 intake manifold, I bought an ECZ-B intake manifold.

Not long afterwards, I discovered that the short block in my 55 was a 56 ECZ-A. At that point, I was no longer concerned about keeping the car original. 

When I decided to replace the 57 Tbird distributor with a CRT, I decided to sell it. I thought I could get a handsome amount for it (based on the outrageous prices I had seen on eBay). However, I ended up selling it to a fellow member of the Sacramento Valley Classic Thunderbird Club who owns a 57. Although he said that he wanted it for a spare, he could have resold it for profit. I used the proceeds to buy the CRT distributor. If my car had been a 57 instead of a 55, I would not have parted with the 57 distributor.

I installed the 57 Dist in my car.  I don't have the vacuum advance connected, because I haven't modified the carb yet. Do I need a fitting in order to connect the vacuum hard line line into the distributor?   I have a fuel filter fitting screwed in now, but I don't want to use this long term.