i bought this 86 olds with the 307 and it had the power master breaks got a vacuum setup in im almost done just need to hook the vacuum up to the back of the carb but i have been looking for days and cannot find the fitting that connects at all im not even sure what size it is its right on the back of the carb a bit lost

 

Remove the carburetor and take it with you to the local hardware store. Find a 3/8" hose barb that fits the carburetor and you'll be set.