Thanks everyone for your help. Sorry for not indicating that my car is a 48 Plymouth Special Deluxe Coupe of unknown history. With your help and some research, I've concluded that the carb is probably close to a D6H1, probably slapped together. To really assess the carb, I will need to remove it and examine its operation more closely, especially relative to the fast idle linkage. I also bought a 1946-1948 carb and air cleaner off ebay in hopes of restoring the engine to stock. I'm also not sure whether the engine is original or not. I need to check the engine serial numbers. The car has been lowered and I'm seriously considering getting back to stock height. I may need some advice on that in the future. Meanwhile, I'm going to go to the El Segundo Driving Museum where they have 50 or so vintage cars on display. I'm hoping they have a 46-48 Plymouth or Dodge that I can examine more closely. Also, I'm heading to the Long Beach Auto Swap Meet on Sunday to get back into the correct mindset.
Thanks again for your help.