So how would you interpret it if the needle was a dozen ticks or so past 120? It was a 390 mill!
I don’t doubt that your car had serious power ,, a 390 would make about 330hp (gross) , my 1970 cougar made 290 (net) A HIGHER AMOUNT ,, My cougar would top out around 120 ... your car had WORSE aerodynamics and more frontal area ...
AERODYNAMICS make all the difference in top speed ... My 1986 GTI with only 102 hp would top out at 116 , virtually identical to my cougar with 3x the power ... my MBZ 300E would go about 130 on under 200hp ...
I currently have a P71 Crown Vic ,, it runs 130+ without a light bar and 114 with a light bar...
My Cougar would bury the needle way down the dial in never never land too , doesn’t mean that it’s accurate... The “certified calibration” speedo in my Crown Vic reads exactly 5% slow at all speeds because it is electronic it’s inaccuracy is consistant,, My 1970 Cougars speedo got progressively AND MASSIVELY inaccurate at high speeds because it was the older tyle with a drive cable and a spinning magnet drive for the needle. I have seen NOTHING but inaccuracies in older cable driven speedo’s at high speeds ... If you want accurate speed readings get a GPS for the dash...