Cadillac Carburetor on K20 Suburban?

[chewiebarker]

Can anyone help me figure out/confirm whether the Quadrajet carburetor on my 1971 K20 Suburban (manual) is the original carb or not? Also whether this carb, if not original, is a cause of bad performance on a Suburban vs. its intended purpose?

In the pic you can see that the number is either 7042237 or 7043237. The number is then followed by 1662.

I tried to look up these numbers online and can only find something on the first 7042237. According to several sources, including Cliff's High Performance, the:
70 = Rochester
4 = 1970-1975 era
2 = 1972
4 = Quadrajet 4BBL Federal Standards
3 = CADILLAC
7 = Manual

Obviously, if there are no exceptions, this is not the correct carb. But I was wondering if these are strict standards or whether, for instance, a Sub like mine built in JULY of 1971 might end up with a 1972 year carb. Or whether GM interchangeably, or consistently, used carbs for subs from caddy's. I already confirmed that my block is a Vette block, so...I don't know.

Finally, should I rebuild this and use it, or look for something specifically designed for my Suburban? I don't care so much about 'matching', I don't think my truck will ever be a showcar, but I do care as to whether it is performing properly. It definitely needs a rebuild for proper operation, I just don't know whether a caddy carb is supposed to work with this truck.

Thanks for any insights. I appreciate all I learn on this board from all of you!