That would be a ‘No’ on being side specific for the dual exhaust equipped vehicles.  To the best of my knowledge, the U.S. 1954-1957 Fords and Mercury’s with dual exhausts had the heat riser valve on the right side (passenger side) of the engine.  Reasoning for this is likely due to how busy the engine compartment is on the left side due to column shift, steering box, clutch linkage, etc.  As a side note, it’s important that the bimetal spring that operates the valve movement is installed correctly.  If installed incorrectly, the valve will be open when cold and then start closing as the engine heats up.  Just the opposite of what it's supposed to do.

Lorena, Texas (South of Waco)

Thanks Ted. Does it make any difference which side it is on for the Fairlane models with factory dual exhausts?

The heat riser valve at the exhaust and the crossover tube within the intake manifold really do have two different functions.  Those cars that had a manual choke still required the heat riser valve but for a completely different reason other than being required for an automatic choke operation.

By design, the heat riser valve located at the end of an exhaust manifold is designed specifically to force exhaust flow through a special passage within the intake manifold which in turn heated the carburetor.  This was to prevent icing at the carburetor which happens at the dew point temperature and is not necessarily anywhere near the freezing point.  Depending upon the humidity, the dewpoint temperature that creates most of the carburetor problems would be in the 40's- and 50's-degrees Fahrenheit.  Icing was a major issue as it did not only create fuel mixture issues, but it could also keep the throttle from completely closing which posed a serious driving hazard.  The heat riser valves were used on vehicles of all makes well into the Seventies although the automatic chokes had long switched to other means in which to operate.  There was a point in the late Sixties where the exhaust heat riser valves were being discontinued in favor of heated air going thru a flexible tube going directly to the carburetor thus eliminating the need to direct the exhaust directly thru the intake manifold at startup.  With those setups, there were air operated flapper valves located at the air cleaner to control the amount of heated air coming from the exhaust to the carburetor.

The air tube within the intake manifold is specific to the automatic choke operation.  For the Fords, 1958 was the last year the intake manifold air tube was used for this as the heat source for the choke switched to the right-side exhaust manifold in 1959.  For the FE with three deuces and the dual quad setups, the heat source for the automatic choke came from the left side exhaust manifold.

Lorena, Texas (South of Waco)

Well, I think it has more to do with how the car will be driven/used either as a driver or something pumped up.

If you have a street driver or restoration, I would imagine one would retain the feature, especially if the wife or daughter drive it. If street performance, the fuel curve will most likely be rich enough so it won't be as noticeable.

I think MUMMERT went this direction as the intake is meant for performance (raised carb pad/runners).

Now the BLUE THUNDER kept the feature I believe but have never seen one, A photo shows one end of the cross-over as being blocked and the other appearing open but than again I see a provision for the crossover tube.

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As was mentioned, living in a cold-climate region is a consideration; however, the Mummert aluminum intake manifold has no heat crossover. If you don't live in a cold-climate region, or do not drive your car at/below near-freezing temperatures, I don't think you'll have reason to be concerned. On cold, not freezing days, it might take a bit longer for the engine to reach normal operating temperatures. Regardless of the crossover or type of choke you might have, running the engine for short periods of time without it reaching normal operating temperature is not a good thing, no matter the make, model, or age of vehicle (unless it's an EV). 

As for condensation in the exhaust system, that is natural, (especially in high humidity areas) if not driven long enough to heat expel it (all short trips - little heat).

Do the service replacement mufflers have weep holes drilled?

Does yours have bumper exhaust outlets?

As for the heat riser valve itself, there would be no difference if mounted on either side (duals).

The way cataloging reads - FYB

1955 FORD - ?
1956 FORD - RS
1955 BIRD - LS
1956/57 BIRD - RS

Everyone run out to the garage and report ...

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"Does the crossover heat tube need to be blocked off if it is not rotted? Mine was a stainless replacement that I pounded in years ago."

No. As long as the tube itself is intact, there will be no exhaust leak (if the manifold crossover tube openings have not been wallowed).

Now here is the problem. If one defeats the heat riser valve, there will be very little hot air (exhaust crossover) under the intake manifold carb plenum to atomize the fuel charge properly and also the hot air choke draws the heated air from that source (via the crossover tube). The choke may not release fully or be slow in doing so. The heat riser does more than just provide hot air to the choke. 
 
All of this also depends on where you live and what weather conditions you experience. While the ambient temp may not get very low, the humidity may be high and possibly lead to icing.

FORD installed this system(s) on most cars so it would be drive-able under most any condition.

Choke settings were usually adjusted for winter and summer operation. The heat riser valve itself was also lubricated with a special lubricant to keep it from hanging.

What gets me is the RS inlet pipe hanging low. Did the vendor offer a choice of pipes, one with the valve and one with the valve removed?

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Does the crossover heat tube need to be blocked off if it is not rotted? Mine was a stainless replacement that I pounded in years ago.

The 55-57 Tbirds have the heat-rider valve on the right/passenger side; the choke is on the same side, whether it's for a Teapot carburetor or 57 4150. Even if you have a full-size, it doesn't make sense to me to have the heat-riser valve on the opposite side of the choke. I have a modern carburetor/w electric choke & Sanderson headers. The ECZ-B intake manifold heat crossover is blocked as well. 

I replaced mine with a spacer, but if you are having problems with the pipe hitting you can get rid of it.  You will have to thread the stud down further or add spacers  between the pipe and the nuts to make up the un-threaded space.  The studs usually are not threaded all the way down when the valve was used.

54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ