I would look at the pushrods. Get the tool to measure what length you need. I'll explain why if i can. The lobes of a cam are round to start with and can only be so big. When they grind a cam they grind the circle into a lobe. Now if you want more lift and you start with the same size circle you are going to have to relocate that circle on the cam shaft. Offsetting it. So now the circle moves upwards and the grind that into a lobe. Now when your valve closes and it is in othe bottom of the lobe there is now play because that base of the circle is moved away from the spot the original cam lobe was located. I hope this make sense. I wish i could draw a picture.