AFB fuel bowl fitting - What thread type?

I do beileve it is 5/8 X 20 as listed here on Edelbrock.com ; http://www.edelbrock.com/automotive_new/mc/install_items/general.shtml

They also show a 6AN fitting. I know it's to small, 8 AN is 1/2 inch. There is a dual feed set up for these carbs. You'll have to drill and tap the drivers side of the carb to use this item. I'm not sure if it is what you seek or good enuff for your use.