What size carb is everyone running on their 383

Mike, it it has a metering block in the back like in the front, it's a 780. If not, it's a universal aftermarket 750. If you post a picture, we can tell you.
Hell, that high didn't last long, my 50 dollar Holley is a replacement, no metering block on both ends , but a good carb to rebuild and put on the shelf I guess, manual chock also