The inner is the one that you don't see from the outside and it goes through the windage tray. 65-71 47751N or 47740 for 72-74 that had the mounting bracket. Lower tube(presses into the outside of the block) for 66-74 is 47768N. Then if you have air conditioning you need extension 47774N. Stick 5013N(19") or 5014N(31") for air conditioning. These are Year One numbers.
Jim