For the Spit project, I've got a choice of 3 stock differential ratios that I can choose from: 3.29, 3.62 and 3.89.

Doing the maths, I wind up with a top speed of 154mph with the 3.29, 140mph with the 3.63 and 130mph with the 3.89.

What sort of speed do you think a 170bhp 750kg Spitfire could obtain, and which would be acceptable for normal street use?