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It still has 4 vent lines, they just come out the rear drivers side of the tank. Theres 1 line off a vapor seperator on the shock crossmember that takes the vapors to the engine compartment. You should (at the very least) put a little mini filter on that line, if your not going to plumb it into the engine via manifold or valve cover breather. Theres no need to swap the tank, and a 71 tank will not help.
As intended? It was never intended for the fuel tank venting to be directly connected to any carb port. How is the hot starting on hot days plumbed as described? There is a reason the charcoal canister is still in use today. The ’73 and later OE carb timed purge port is balanced, the timed port for vacuum advance is not balanced and is not intended to be used as a purge port.
An intact evaporative recovery system/fuel tank vent system, as originally designed, is not a detriment to performance in any way.
71/73 tanks are physically the same, with just differences on the vapors system. If you are not going to use it, you can use any one of them on any 71/79 model.
Mopars on Vzla never got the vapors recovery system and used same tanks you got, so that won't be a problem.
74/79 are diff monsters and won't fit on 71/73 due the hump on tanks used for vapor system redesign.
The next diff will be if single or dual exhaust. Single exhaust are tipically used on low perf cars and they are wider on left side. Repros are anyway all made to dual exhaust.
71 didn't have a charcoal canister. The line from the vapor tank in the fender well went to the 3-nipple cap on the valve cover and then to the carb bowl.
To be clear, the enclosed carb bowl vent nipple does not intake or collect fuel vapors. The fuel bowl vent valve is another source of evaporative emissions to be collected while at rest, for ‘71(and California ’70), these vapors were stored in the crank case to be consumed/purged though the PVC system on start-up. Connecting the fuel tank vent line directly to the float bowl vent valve nipple can only lead to fuel vapors collecting in the air cleaner at rest, normally resulting in hot start issues for a correctly tuned motor.
The one year only ’72 four-nipple charcoal canister also purged through the PCV line, ’73 and up 3-nipple canister depended on a dedicated timed and balanced purge port on the OE carbs to route the stored vapors to combustion.