That is a good question and I don't know the answer.

Stretched limos generally are production cars that have a section added in the middle. The suspension is strengthed to hold the extra load but I think the engine and body parts of both ends are original. I would bet that they are titled according to the original car. I built a hot rod as a youth - custom frame and suspension, buick engine and model A ford from the firewall back. It was titled as a model A ford.

For non-stretched limo (older cars) I think some were made at the factory but most were probably bodied somewere else. In the 1920's and 1930's it was common for big fancy cars that the car maker sold a rolling chassis and some other coachbuilder made the body. For example, I don't think the Duesenburg factory made anything but a chassis + engine - I don't think they made bodies at all. But all of them are known as duesenbergs.

What I'd like to know, as far as custom limosines go, is both how they're registered with various licensing agencies (what car are they legally recognized as), and how much of them is production model - do most limos roll of the factory line as a certain car, and have the extra bits spliced in the middle, or is there not a single chassis bit shared with the models it resembles?

OK, "antp", I promise I won't ever complain again when you allow these stretched Cadillac limousines to be identified as "DeVille" or "Fleetwood" models. I'll just snicker to myself in the knowledge that all of you are mistaken! The last of the 7-8 seater "75" sedans and limousines were built at the Cadillac factory 20 years ago, 1n 1987. A few "stretched" limiousines were built after that, with Cadillac approval, by Hess & Eisenhardt (e.g. the "Presidential" parade cars). All the rest are custom jobs by independent coach builders like Armbruster, Gaines, Moloney, O'Gara, etc. These do NOT qualify as "DeVille" or "Fleetwood" models.

Cadillac officially made some Limousine, so the stretched ones cannot share the same name I think.

i voted for adding a stretched category....assuming it's for cars that have been cut in 1/2 and added onto to make longer...and that way we just name them Lincoln Town Car Limo and Cadillac DeVille Limo.

There are some car that were designed to be primarily used for limousine purposes rather than a private car, for example the Soviet GAZ Chiakas and the ZILs were never available for sale for anyone with the money, the same way a Rolls Royce is, they were exclusively for senior government officials, even if a Soviet civilian had the money, he couldn't have one. A Daimler DS420 is different to a Bentley Arnage, although that is a very expensive car it could still be used everyday and for leisure, the Daimler on the other hand is not exactly a car you'd drive yourself. I wonder if the new Rolls Royce Phantom and the Maybach are limousines or just sedans? The Maybach 62 has to be limousine, if you wanted a sporty saloon/sedan, you buy an S-Class instead.

current

I think its probably OK. I was just pointing out some of the inconsistencies in the classification of vehicles from my point of view.

I guess the US is different regarding trucks, I guess the main difference is that trucks (including pickups and many SUVs built on truck frames are classed as trucks and do not have to meet all the safety standards that are mandated for cars.

If I had to separate them your explanation may be best e.g. commericial and non-commericial trucks.

In Europe they are less common, so I am not very sure.
The limit between a real "truck" and a car is the weight. I do not know for other countries, but in Belgium the "car" driving license allows you to drive 4-wheel vehicles of max 3500 kg with max 8 passengers (+ the driver then).
For the tax, they can be (but it is optional) less taxed because they are commercial vehicle, but it also works with any car that is declared as commercial, i.e. where there is more than x% of space available for goods, and that this space is separated from the seats by a fixed panel or grill.

Maybe that the "truck" category should be renamed as "heavy trucks" then?

I don't know about europe but in the US pickups are built, sold, registered, licensed, insured, and taxed as trucks -Granted some may be small trucks but they are trucks nevertheless.