That is strange that there would be a number 7 in that position. Usually it is a 1 or 2 for federal carb ID, or it is a 4 or 5 for california emissions carb ID. Are you sure that is the number. {sometimes a 2 looks like a 7 if the stamping is not even} Oh well, maybe Cliff knows. {hey Cliff....}.
As far as using this carb for a pontiac with an automatic, it depends on what automatic. Some trannys have a "kickdown cable" {early turbo 350} or cable for throttle pressure {latter turbo 350}. Your carb may or may not have the place on it to hook up the cable for the trans. Anyway, whatever trans that you use, if it has a cable coming from it , this must be accomadated for on the carb linkage. Sometimes this is easy to adapt for and sometimes it is not. If it is not, you may consider sending the baseplate to Cliff to have it modified. Either by changing out the throttle shaft or having the appropriate mods done to yours if possible. So, there is always a way to make it work, the question is how much aggrevation and money do you have to go through to make it work. The turbo 400 does not have a cable so if you have that trans you're good to go.