Gas tank hook up 71demon

Look this up in the service manual. There were changes almost every year from 70 and later for the evap emission controls. Only CA cars in 70 had it and possibly 71. First year or two had vapor separator in trunk, then tank was changed and separator was eliminated

NO A BODY uses a vented cap. The evap control cars use "pressure vacuum" relief caps which are NOT the same as vented. The car MUST have a vent. On the emission / evap it is provided by the line going "up front" to the carbon can stuff. You can NOT eliminate that without replacing it. You can NOT eliminate the vapor separator without causing siphon/ leakng problems.

I've said this before. If you are modding a vapor / tank controlled car, best idea in my mind is to mod the filler neck to mimick the 69/ earlier vent.

The filler caps pictured above are telling....about the changes

Best thing I did for fuel boil/ vaper lock was 1...rear mount electric pump, 2....carb isolator spacer........3....fuel / vapor return. Use a Wix filter with the orifice. 33041? 33042?
Go to mymopar and download the 69--73 shop manuals and read them.