My 49 Merc M68 has te single pole temp sending unit on the driver's side head above cylinder #6 and a threaded plug in the outlet above #7. The 2 pole sending unit is on the passenger side head above cylinder #2 and the shut off valve for the heater in the outlet above #3.
This is a Canadian truck and I have no way to know if this was the original set up but it certainly looked like it was original and had not been altered.
I'll try to post some pics tomorrow.

49'er

 

Heres a picture of the heads from my 49 Merc. You can see what looks like a standard plumbing plug in the outlet above the # 7 plug hole on the drivers side head (the cleaner one!). The single pole temp sending unit was in the front oulet above plug hole #6. The passenger side head was not cleaned up in this photo but the front outlet had the double contact temp seding unit and the rear one was the shut off valve fot the heater.

49'er

 

Feedback I got on the flathead forum is that all export models in Australia (made in Canada) came this way. But the extra hole seems to always be plugged, so not clear why they are that way.

There isn't an "idiot light" for high temp on your truck, is there, 49'er?

 

I think we have a winner! 52 Merc pointed out that the RHD models exported to the UK and Australia were Canadian manufacture. For RHD, the heater would go on the left side of the cab, so they had to put two ports on the left head.

 

49'er

The Aluminum Heads you are showing are not Mercury, they are 49 Ford.

The 49 Mercury had the designation Code C8CM. The one shown with the 2 ports is the Passenger's side Head, and the one port was used for the Hot Water Valve. The Heads are not interchangable from one side to the other as they last were in 1948. Also the Mercury Truck did not have the Merc Engine as some believe.

To tell the proper designated Heads for rigt or left side are as follows and they should be embosed on the head.

C8CM 6049 A-Right Hand Cast Iron
C8CM 6049 B-Right Hand Aluminum

C8CM 6050 A Left Hand Cast Iron
C8CM 6050 B Left Hand Aluminum

(Mercury)

8BA 6049 C Right Hand Cast Iron
C8BA 6049 Right Hand Aluminum

8BA 6050 C Left Hand Cast Iron
C8BA 6050 Left Hand Aluminum

(Ford Cars & Trucks from Serial # H48-20001)

The later 1949 Ford Trucks had the 8BA Engine, where the early still had the 59A Blocks.

 

49'er


Just recalled what that part was that you took out from the head, have seen them before and should have put it in my last post.

Block Heater, even though its not in the block that is what it is.

P.S. those aluminum Heads you have there, guys are looking for these if your going to sell them.

Your about 60 miles from me.

 

Thanks guys for clearing this up.