What did this come off of?

[Blu Dice]

Can this work on driver side of a EAB?

 

[51 MERC-CT]

Sure looks like it might. Never have seen one without the cross over fitting.
Maybe aftermarket or for a 3 cyl. engine

 

[Blu Dice]

Has SM 591 cast on it. I know there are guys with books that can look this up.

 

[41Joe]

I just found this online.
http://shoebox-central.com/1949-1951-ford-v8-left-dual-exhaust-manifold-usa-
You'll have to paste that link into an address bar, but it shows it as a 49-51 driver side manifold.

 

[Blu Dice]

I read they were used on police cars.

 

[Bruce Lancaster]

It is an aftermarket manifold to facilitate putting duals on a late flathead. 2 different ones covered '49-53. The one you have is reproduced by Drake, and you can get years of application on his site.