Mils,
You'll probably need help.
https://www.holley.com/support/carburetor/
Exploded views and then MORE. Find 4150/4160 as most likely what you have or at least close. Then you should search out tuning books on Holley carbs. HP Books does a pretty good job, there are others.
Vent whistles are inside the float bowls attached to the metering blocks. If you haven't disassembled the carb you won't see them. Otherwise they are hollow plastic (white) about 1/2 inch wide, 1/8 inch thick and 1-1/2 inches long. They press into the metering blocks, usually a friction fit.
Jim
The solution provided by Argess may solve the problem. I didn't have much luck with the connecting tube fixing my braking issues. Strange enough the engine didn't die or even stutter when hard braking in reverse.
BTW a new carb may help but may also force you to learn how to tune the idle, main and secondary circuits. Don't forget power valves and air bleeds.
Got any local OLD guys that know how to tune a carb? Most of the younger guys falter if they can't hook it up to a confuser, er. computer.
Jim - certified old guy.