I've had a vacuum gauge on a couple of my cars (trucks) in the past, but do not have one on my Model A, (or my newer cars either) presently
Most noteably was on a 71 Ford Pickup with a 429 engine. I used it to keep my foot lightly on the throttle, especially since that thing would really scream when asked to do so. It was great when pulling a trailer in the mountains as a tool to tell me when to downshift. (C6)