In this picture, left to right, and top to bottom is:
1968 - 7028268 (400/auto)
1969 - 7029268 (400/auto)
1970 - 7040263 (400/mt)
1971 - 7041264 (400/auto)
1972 - 7042264 (400/auto)
1973 - 7043262 (455/auto)
1974 - 7044268 (350/auto; GTO c/w at bracket)
In the foreground are the two types of bolt on theottle cable brackets I have.
For those who don't know:
1) 1967-1971 used a biolt on throttle cable bracket;
1972 was the first year of the throttle cable bracket being fixed to the primary throttle shaft.
2) 1969-1972 (with some exceptions) used one of two versions of Pull Over Enrichment (aka: primary squirters).
3) 1967-1972 used a divorced choke mounted to the intake manifold;
Starting with 1973 the chock was attached to the carb.
4) the 1971-1974 style fixed fuel bowl vent was introduced (albeit in a modified form) on the 1970-California carbs (third digit from the right/end would be a '5'.).
From my experience, at least local to me, pre-1977 carburetors are extremely tough to find - the older the harder they have been for me to find.
I also have one of both 1975 & 1976 455(auto) carbs, currently have two 1977 400(auto) carbs, and one 1978 400(auto) carb, as well as one 1980 301-Turbo carb.
Now, finding pretty much any Pontiac carb in the wild is nearly impossible.