Hi Dave,
Your 70 doesn't use the small vacuum vent in the base that's mentioned above, that's a mid/late 69 CJ thing. (it delays the opening of the automatic choke on a 69, your 70 uses a manual choke cable)
The 70 base uses a plastic elbow and rubber grommet for the crankcase vent hose instead of the metal tube that the 69's use. The biggest difference (and what makes a 70 base such a pain to locate) is that there's an extra recess stamped for additional clearance around the throttle cable/carb linkage. I attached a pic from the 428 site to show this. (I circled the area in red) I have an early 70 (9/11/69) Metuchen Survivor/barn find/turd that's surprisingly original and it has this 70-style air cleaner base so I'd bet yours is supposed to have the 70 style also. The air cleaner is part of the approved emission system so I'd be surprised if Ford would use 69 model year parts on a 70 ... Hope this helps, John