The specs on the second link do not mention weight, but I imagine that the thing weighs somewhere north of 6,000 lbs. I make that guess from the fact that my sister-in-law's hubby Gene is a classic car collector who primarily collects Packards of the pre-WWII era. They are amazingly beautiful cars, with (like the Delahaye) with a body hand built on a chassis which was the only thing the buyer got from the car manufacturer. However, they are all heavy, weighing between 6,000 - 7,000 pounds in finished form. With their straight 8 and V-12 engines, the Packards are significantly faster than the Delahaye, however, they're nowhere as fast as one might suspect. Weight was then, as now, the enemy of performance.
Also, the output of the engine was very anemic by modern standards at 37 BHP (brake horsepower)/liter of engine displacement. I'm considering buying one of Ford's new Fiestas. That car has a 1.6 liter engine that develops 120 BHP. Doing the math, that comes out to 75 BHP/liter - twice the power output of the Delahaye. If that 4.455 liter made the same BHP/liter output as the Fiesta's 4 cylinder engine, it would make about 334 BHP instead of 165 BHP.
The Delahaye's engine is what is known as an undersquare design; that is, its cylinder bore is less than the vertical stroke that the piston covers in one revolution. In addition, it has an older overhead valve design with the camshaft in the engine block. The Fiesta has an engine that is oversquare; that is, the stroke is less than the cylinder bore. The result is an engine that can operate at higher RPMs. It also is a double overhead cam engine (DOHC), with the valves being directly opened by the camshafts instead of through pushrods as in the Delahaye (DOHC engines existed at the time of the Delahaye, but were almost exclusively used in racing applications). Add to that better fuel management through fuel injection as opposed to the Delahaye's carburetors and modern electronic engine controls, and you can see clearly why the Delahaye was horsepower challenged.
But, DAMN, IT'S ONE LOVELY CAR!