I have a 64 230/3spd/3.73, been driving it 70 mph on the highway. I checked my speedo/odo w/a GPS. I have 225/75/15s all around. I was worried at first it would be too low geared but the six seems just fine, although it don't like going any faster than 75. Brian

My \'64\'s in the Gallery
Pictures in my Photobucket
1964 C10 Custom Cab 350/700R4
1964 Suburban 350/700R4
1979 Ford F350 4x4 400/c6