None of those numbers is the carb number—on Carter BBS carbs like this, the carb number was stamped on a triangular aluminum tag attached by one of the two front screws holding the top casting to the middle casting. This tag usually goes away during the "remanufacturing" process, and judging by the painted choke pull-off and raw, sandblasted castings and levers (passivated casting surfaces and plated hardware are now stripped bare and ready to corrode and rust) this is such a carburetor.
This what you've got is a '70 (California) or '71 (50-state/Canada) passenger car carb, or could also be a '70 (Cal) to '73 (50/Can) truck/van unit. In good shape, this is a better carb than the one that would have been original to your '75. Order a good-quality rebuild kit for a Carter BBS 4956s and you'll have everything you need. This isn't quite that carb—its hot-idle compensator is blocked off, maybe by the factory and maybe by the "remanufacturer"—but the kits are generic enough that close-enuf gets the correct kit. The parts store kits are nowhere near as good as they used to be. The best kits I'm aware of these days come from
Daytona Parts. None of the kits comes with a proper float gauge any more, all you get is a useless strip-of-paper pretend ruler. This matters, because it sounds like at least one of your problems is improper float height (float wear is not likely, but the float must be checked to make sure gasoline hasn't got inside and made the float heavy). One workaround is to also buy an old-stock kit off eBay and rob the float gauge out of it. Another workaround is
here. Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted
here for free download, and also look at the tune-up parts and technique suggestions in
this post.
Also, it looks like you might have the wrong base gasket between the carb and the intake. Can't see for sure, but that looks like a '73-up base gasket, which is not properly compatible with this '70-'72 carburetor you're running (the later gasket does'n't have the needed vacuum routing passages). The carb kit should have the right base gasket—it's about as thick as this one you have, but it's shaped a little differently around the throttle bore.
New to carbureted old cars? As soon as you can, get the three books listed in
this thread.