Unless you are trying to restore your 71 to perfectly original I would not order the 4 vent fitting tank, the single vent tank you have now is superior. All you need to do is splice the single vent into the line that goes up to the passenger side fender in the engine bay. You can simply cut that line near the vent in your new tank and splice into it. At that point you can remove the vapor canister thing from the driver's side of the trunk and discard it
Just to be clear the vent line that goes to the passenger fender in the engine bay runs right along the front of the tank so very easy to cut and splice into.