FortyFord2, I had a flathead ford with 4.11 gears that screamed at 55, went to 3.78 and it screamed at 60. went to 3.54 and it screamed at 65. You can gain a lot more streetable car with an over drive tranny if you can find one (think we have a 51 vintage one, but it has always been contrary. Seems as though we could never get the selonoid to work every time. When the overdive worked, it was a totally different car). We have since put a 302 in it and installed a later model OD tranny. Now it will cruise at 75 all day.