This is a 1952 or 1953 Dodge truck. As best as I can tell, the hemi V8 was first available in Dodge trucks in 1954 (1954 Dodge truck CC here). Chrysler also built some really big flathead sixes, for the big trucks and other industrial uses. That family started in 1937, and went from 282 cubic inches all the way to a mighty 413 inches, in ’53 – ’54 trucks. These were physically much larger engines than the Chrysler automobile and light-medium duty truck flathead sixes, and they had 12 ports and dual carbs. The 413 was an absolute torque monster (424 lb.ft.), and was rated at 177 hp, almost the same as the 331 hemis in these Chryslers. Here’s a picture of that mighty flathead:
As I said, it had 12 ports, unlike the passenger car sixes, and genuine split manifolds for both the intakes and exhaust. On the 413, bore was 4 1/16′ and stroke a mighty 5 5/16″. It had a rep for a bit of a drinking problem.
Of course that Dodge truck could be sporting the 111 hp 250 six; there’s no easy way to tell from this picture.