Errrm not quite CaverD3,
Close though and it is all pretty mind bending and confusing stuff
TBH it's nice to see someone taking an interest in such stuff and i am always happy to help anyone interested to learn a bit more about their vehicles and what makes them work.

Quote:

standard or extended addressing prototocols that are clearly defined as either 11 or 29 bits long.

As stated, the bit difference in question is a difference in the bit length of the addressing, ie the header part of a CAN bus message. This makes the two distinctly different and not cross compatible. Every single ECU on the CAN buss's of a D4 have different addresses and node identifiers to a D3. The new node addresses are of course 100% Ford compatible

Those less technically interested may want to stop reading about now

For example, 7E0 is the 11 bit addressing equivalent of 18DBF110 in 29 Bit addressing
Both contain the same elements of Bit by Bit prioritization, Message type and to / from identification, which is why i can recall such values from memory alone and easily pick these out from the many other bus messages as being Diagnostic messages sent from a tester to an Engine Management ECU, Quite sadly i can also read the rest of any such headed message and tell from memory what is being asked for or responded with.
I only wish i could remember the wifes birthday our our anniversary

Loss less message prioritization on CAN is done quite cleverly IMHO,
Suppose two nodes (ECU's) start transmitting a CAN bus message at the same time, one with a 7 at the start (Binary 111) and one with a 6 (binary 110)
Both assert the first 1 on the bus and read the bus state to see that 1, then they progress to the second 1 and everything is still fine, however on the third bit, only the ECU transmitting 7 (111) asserts a 1, and is happy to read the bus state and see all is well, however the ECU transmitting a 6 (binary 110) ant therefore not asserting a 1 sees the bus as having a 1 on it and so knows another ECU is simultaneously transmitting a higher priority message, and stops transmitting for the length of a message before retrying. Hence the higher priority message gets transmitted with no need to repeat and no time loss.

The bit rate is something different and remains at 500K for the high speed CAN bus in both addressing cases.

This means speed is not really an issue as Buss's for both addressing types and both typically have 2,500 messages on them per second, in fact, to keep all messages the same length they are typically padded out with a lot of zero's. If anything the 11 Bit Addressing would be faster anyway.

The addressing on the lower speed CAN bus also changes from 29 to 11 on the D3 to D4.

Hope this helps