Hi, 1st post on this forum.
The Camsahft endplay if I remember right should be between .001" and .007" with a limit of .009". So with the thrust plate on, the cam should move back and fourth ( In & out) this far measured with a dial indicator.
So if it sticks out before putting on the plate something is wrong. You don't need a spacer if the endplay is O.K. , but you have to check it.
The one from Summit is a roller thrust plate it has a torrington roller bearing on the cam side, notice the cutout on the plate? I have a Danny Bee Racing one which has the same thing, so the front of the cam rides on a roller bearing instead of the flat metal plate.
Summit says it's for a SVO block but ALL small block cams will fit so I don't know what exactly is different for that plate. If it would fit it would be a great buy!