OK, the hobby shop I went to had two different versions of the Shinano with two different kit numbers. I have to check the box again for the 31215 number - there is also a different number; 2200 on one, I think 2600 or 2800 on the other? Anyway, one was $39, the other was $29! I bought the less expensive one, not to be cheap, but because it had the lower number and I was hoping that it would be the older kit. I can't vouch for the other kit, but the one I bought seems to have the right parts.
As a side note, it is a pretty neat model. I would almost consider getting the newer version just to build it.
There was no trace of the wing-hub braces that I am looking for, or any other parts that I could recognize from the bomber.