If Stock it is a 600 CFM Holley 4180. The 4180 was a smog carb that was built by Holley for Motorcraft. The tag on it is very important if you ever have to rebuild it. It contains a Motorcraft # NOT HOLLEY#.
Since this is an 86 Bronco, I guess the carb was built in 85.
I am going to get the Holley rebuild kit and give it a try.
The carb has not been much trouble over the years, except it will not pass a gas station, about 10mpg around town.