Drag increases with the square of velocity, so you really need to be slippery in the air if you want high top speeds. Because every mph of added speed adds more drag than the mph just before it.
In fact, power-weight ratio mostly affects acceleration, while top speed is driven by horsepower vs coefficient of drag (and frontal area).
My motorcycle (2001 650cc V-twin sportbike) was considered pretty low powered for a sportbike at only ~66 hp, whereas 600cc 4-cylinder bikes of the era were putting out 100 hp and 1000cc 4-cylinder bikes putting out maybe 140 hp. But it apparently it was rated at a 0-60 time of ~3.4s. Which puts it in modern very high performance sports car territory off the line, and WAY faster than any of those muscle cars. But it also topped out just over 130 mph, because motorcycles are an aerodynamic nightmare. A 100 hp 2001 GSX-R600 would get you only about another 25 mph, top speed reportedly 158 mph. Throw another 40 hp on top of that for the GSX-R1000, and you get to... 173 mph. (All numbers from Google).
The muscle cars of those days weren't designed by computers an optimized for wind tunnel performance the way things are today.
Modern Sedan Cd: 0.30-0.35
Muscle Car Cd: 0.45
Estimated MotoGP Motorcycle Cd (with rider): 0.60
So yeah, I'm not surprised a muscle car tops out at 130-135 mph despite the big engine. The coefficient of drag AND the frontal area are both pretty terrible.
You and I had this discussion before but I'm adding it here for
@SFBadger96 :
The last two classes of Battleships produced by the United States were the South Dakota Class and the Iowa Class. The US built four SoDak's and four Iowa's. Construction began on all eight prior to the US entry into WWII (mid-1939 through early-1941). There were another two Iowa's planned but they were not laid down until after the US entered the war and they were never completed.
Anyway, the relevant issue here is speed. Both the Iowa's and the SoDak's had a main armament of nine 16" guns. To be fair, the Iowa's 16" guns were somewhat better as they were 50 caliber rather than 45 caliber for the SoDak's (this refers to barrel length as a function of diameter so the Iowa's barrels were 800" [16*50] while the SoDak's were 720" [16*45]. The ships also had more-or-less equivalent armor protection schemes and an identical secondary battery of 20 5" guns.
The major difference between the two classes was that the Iowa's were a bit faster at 33kn compared to 27.5kn for the SoDak's. That 5.5kn increase in speed came at a tremendous cost. The Iowa's had 212,000 hp and weighed 48k tons while the SoDak's had 130,000 hp and weighed 35k tons. The bulk of the extra weight was for the extra machinery to make all that additional power and the expanded hull size to fit all that extra machinery. So basically the USN paid 13k tons for 5.5 kn.
In theory this was needed because the Essex class carriers were also capable of 33kn so the Iowa's could keep up with them and the SoDak's couldn't but as a practical matter carrier escorts needed AA guns and the 16" guns of the Iowa's and SoDak's were worthless in that role. It was the 5" secondary guns that provided AA coverage and that could be had SUBSTANTIALLY cheaper by building CVL's and DD's.
In the actual event, the primary use of the Battleships was bombarding targets on land and for that the USN would have been much better off with five SoDak's than four Iowa's simply because 45 16" guns are better than 36 16" guns.
Much like your Dart/Muscle Car example, the same is true for BB's. Increasing top end takes a LOT of HP as
@betarhoalphadelta explained.