Question for the K owners: C vs K engine suffix code question

[jocko]

I have a question for those of you with K10s and K20s out there. Below is a filtered excerpt of 72 350 truck suffix codes. Some indicate a K-only application while some indicate a C-only application. If there were no codes that indicated both C and K applications, I wouldn't have a question, but there are (like TDK, TFH, TFJ). So, I "would" have assumed that the K-only suffix code would have indicated to a line worker to install the correct exhaust manifolds, etc - the little bolt-on nuances of a K engine. But since there are some codes that apply to both C and K, I'm curious what the real differences are, if any, between a 72 C20 engine and 72 K20 engine.

Or put another way, what is the difference between a TDJ (C-only) and TDG (K-only) -coded 350?

Have any K owners that have original engines ever noted a C-only suffix code in their K (like a TDJ, TFD, etc)? (or vice versa)

My underlying assumption is that the engines are identical mechanically - and just have different bolt-on additions to make them specific to a C or K model - like the difference between exhaust manifolds on a C or K - but I'm curious if it's that simple - and the presence of codes that apply to both C and K muddy the waters.

For those of us with the purist ailment (and I fully appreciate none of these engines have partial VIN stamps), I am wondering if, for example, a TDJ or TFD coded engine could ever have been "correct" for a 72 K10/20. I'm pretty sure the answer is no, but I'm trying to figure out why that would be the case.
Something to chew on, thanks in advance for your thoughts.
I need to send up the Keith bat-signal...