The 1850 is a universal 600 CFM carb. It never came on a vehicle.
You have a primary metering block from a 4777 650 CFM double pumper. It will not work correctly with your carb.
You are better off getting a 4150 style Holley that came with a secondary metering plate. Or put the metering plate back on. You are going to end up with the carb not metering correctly.