This might be a silly question...

The 318 linkage should work but will probably take some modifying due to it being for a 2 barrel and your car having a 4 barrel. Another question is what trans. does your car have? If it's a 727 the link from the bell crank to the trans shift lever is probably a different length than the one from the Diplomat because they only came with 904 transmissions. That may not be easy to modify.

From now on when you post a question provide details on what your working on because not all are the same. Saves a lot of time posting it all at once