Not sure about fastest 40-times, but Pierre Goode had to have produced some of the fastest 100-meter times for a real football player. Young man had blazing straight line speed, not so much when having to make a cut or move.
And I cannot remember his name, but sometime around the mid-1970s a member of the track team with one of the fastest 100-meter times in the world was brought over to the football team to play WR. To say he was fast is putting it mildly. To say he had hands of stone is a disservice to all the rocks in the world. If I remember correctly, the young man could only be used on the relay units on the track team in the lead-off leg because he could only be depended upon to hand off the baton and not receive a hand-off. Too bad too, because in the days of the wishbone he would always have had single coverage and there was not a DB around who could keep up with him on any route over 25 yards.