3.55 or 3.73 gears in 66 dart gt

IMHO

I have 3:23 in my 67 dart. Highway is no issue.

3:55 is a nice compromise.

My friend has 3:73 in his 67 dart. And he has to lead on the interstate as he is screaming at 75mph.

From an online calculator.

26" tires 75mph (add trans slippage and the numbers are higher)
2.93 = 2840
3:23 = 3131
3:55 = 3441
3:73 = 3615