National features GM products, but that isn't all that they carry. I have seen Toyota Camry's, Nissan Altima's, Pontiac Grand Ams and Grand Prixs, Dodge Stratus and Intrepids, Oldsmobile Alero's and Intriques as well as Chevy Lumina's and Malibus. Last time I was on the aisle I also saw a station wagon. I don't recall what kind, I think it was a Subaru. You may find larger or more luxurious cars on the lot, but it isn't guaranteed. In this case you may find a Pontiac Bonneville, Olds Auroras, Buick Lasabres or maybe an SUV, minivan or a sporty car. But as Pluto4President mentioned all you are quaranteed is what you reserved. Anything nicer should be considered a pleasant surprise. You get to pick whatever is on the lot at the time you are there, so good luck!
I don't recall seeing Ford Products the last few times on the aisle, but I bet they have them as well, maybe someone else recalls seeing them.