I have 4.10's stock in the 86 250, and it will run about 70 with the stock T19 4 speed. If it had 4.56, maybe 45 top speed would be right, but not for normal gears in these 250s. The truck he is asking about is not a big truck. If I were to try to put one in the old 71 F600 I have, that would be more real as well.