Would these carbs be from GM or a speed shop
It's highly unlikely that you'd find a 4053 on the shelf at a speed shop either today or 40 years ago; the 4053 was made for very few specific production applications, vs. the "generic" or double-pumper Holleys usually carried by speed shops. They were available over the parts counter from GM for many years, which is why you see so many of them out there with 4-digit 1973-up date codes on them, and Holley may have made a run of them in the last five years or so for the restoration vendors.
