Top speed on that car? It really depends on the gearing in the rearend. I actually have a 73 Road Runner with a hot small-block in it (400hp), and when I still had the 2.70 gears in the rear, 140 was NOOOO problem. Of course, at 140, on Z-rated low profile modern tires, but old, rickety worn-out suspension, I was scared. The car swayed like hell. Daisy's car in the series is a big-block (they show the engine of that car in the episode called "Daisy's Song"), either a 400 or 440, so it probably had the 3.55 Sure-Grip rear, so theoretically, taking into account engine RPM and redline limit, the car would probably max out at 120-130. If it had the 2.70 rear like my car, 140-150 completely topped out would be possible. God I hate being a car-guy. I read WAY to much into movie and TV stuff like that.
With 4.88s, a big-block, and no overdrive, that car's top speed would be 80-90 Mph, maybe a little more, but not much, but it would sure as hell get there quick. Redline on a stock Mopar big-block is only around 6200-6500...
My first car (as pictured) was a (as titled) a 1973 Road Runner. It had an optional 383 block in it with the slap stick tranny. I got it up to 130 before I lost my wits. The suspention was not good and the front end started to lift and I was losing steering so I backed off. Some of the best fun I ever had. Launching in 1st gear could ALMOST lift the front wheels. I blew the motor at the local drag strip on "Run what ya brung" night. I sold the car for $500 bucks. I regret that day.