No, it is like building totally different vehicles, out of different materials.

Go to youtube. There are several videos on how various things are made. If you look just at automobiles it is amazing how each manufacturer decides when and where to insert the drive-train, the interiors, etc.  who like to buy complete pre-assembled components, or who like to do in-house manufacturing of key components.

The difference between how an A320 is made versus the smaller, composite C series is probably even far greater than I believe.

Different cockpit suppliers, interior suppliers. Do you nee a new paint shop for different plane sizes, curing requirements, and paint types (aluminum versus Carbon fibre)...

Etc., etc.