Sergio Marchionne has publicly ruled out a GM-FCA merger, but the Fiat founding family still seems to want one. If it happens, it will happen with their investment company, Exor, and allied banks taking over an effective majority of General Motors. This would not have to be a complete majority, just enough to get the votes they need.

FCA+GM
GM would not be on top, so we may look at US sales to see what would stay. Buick, GMC, and Cadillac carry higher margins, so even with lower sales, they will (probably) remain. Jeep is also unique and would almost certainly stay.  Dodge is FCA’s Pontiac, and would likely stay now that GM is no longer downsizing.

Now, let’s let the numbers talk for themselves...

gm-vs-fca

There are few places where FCA has a clear advantage, as one would actually expect. Dart seems to be the most endangered species in any merger; most of the others can hold their own, especially when considered as part of an ecosystem (e.g. 300, Charger, and Challenger, which all share a core setup.)