my first experiance with a cam change on a small block saw a failure at the valve lock area. the grooves were hammered out. turns out the bottom of the locks were touching the top of the guide. this cam was 520 lift.
If you use the OEM type umbrella seal all you need to do is trim the tops of the guides some with a cut off. It is not a critical area and don't take a precision cut unless you use teh Perfect ccircle type of seal. Just don't leave any burrs on the inner guide area. There is plenty of guide there that you won't hurt anything.