New solid roller cam sticking out about 1/4"

I am in the process of putting together my 470 stroker and after installing my solid roller cam it sticks out of the block about 1/4" when I line up the cam journals with the lifter bores. Is there a spacer that goes in before the cam? Is that what the cam button that goes on the outside of the cam is for. I noticed on the front of the block where the cam starts to go in a notch on the right side, does a spacer go on before the timing sprocket or is this where the cam button comes into play. Thanks