That does not sound right. There is a slight difference (in a glide the lift is slightly less than weight, so speed will be lower) but to a first approximation the best Lift : Drag speed should be constant, as it depends only on angle of attack (about 4° for a normal aerofoil). Why do you want to know the best Lift : Drag in the cruise? Is that for endurance speed? Not flown the PA-38 but I would be surprised if it was that high.