Excellent carb. All of the 1975 and later Pontiac q-jets (non-CCC) will be the larger castings.
All of them are basically the same from 1976 thru 1979 if they came on the 350 or 400 Pontiac engines. The 1975 models have the one year APT system, and are not as good as the later APT version.
The 301 carburetors are not nearly as good in stock form as they have modifications made for the smaller CID engines. They are however just as good once properly set-up.
I use a 1977 17057274 carburetor on my 455 over 550hp. It is completely "stock" as far as the castings, but of course recalibrated for my engine and using our rebuild parts.
I've had it on the dyno and at the track scores of times and it has outran every other carb we've tested against it. This includes very well set up Holley 4781-2 850's, HP-950's and Demon 850's.
Here's a clip of my car at the track using that carb on a factory intake:
https://www.youtube.com/watch?v=6zVdoLR-VzMI did upgrade it to an electric choke as well, otherwise it has not been modified in any way, just recalibrated for what I'm doing with it......Cliff