What are we expected to do with a muscle car? If we want look cool, make a lot of noise and make fast quarter mile times a ‘70-71 Hemi Challenger (or something similar) would be the best choice. If we want to commute to work daily the previous best choice becomes one of the worst. Those things are ridiculously expensive, thirsty, unreliable and unsafe. Deathtraps can be cool but the best choice for a car shouldn’t be a deathtrap.
A Mustang II isn’t going to go fast in the stock form and most people don’t think that they look cool either (some of course do). They aren’t very thirsty or expensive but still unreliable and unsafe. But because Mustang II is a very tiny car compared to the other muscle cars you can still make it go fast with power upgrades.
So the worst has be something that is overall worst combining: performance, handling, cool looks, purchase value, safety, economy, upgradability
So I’m thinking about something slow, big and heavy from late 70’s. I have never liked the last years of Gran Torino so I’ll choose this one. It being used in Starsky and Hutch TV series does not award positive points from me. It does have fancy safety bumpers but that kind of safety features aren’t very essential with a musclecar.
My uncle actual got into an accident with a ‘72 or ‘73 Challenger while these things were still quite new cars. His car got squished sideways between two heavy trucks. The Challenger got quite badly mangled but the thickness of the doors did provide a lot crumple zones and my uncle did survive without bad injuries. He didn’t describe how did he end up between the trucks but I somewhat expect that he was driving like a wealthy businessman with a fast car…