That engine looks like a T-245 M37 engine from what I can see. Check for a number stamped into the boss directly behind the oil line, located below the thermostat housing and just above the blocks front freeze plug pictured. Look hard, sometimes they are faint and the area will likely need to be cleaned if not obvious. Does the oil fill tube have a bottom flange that bolts to the block, actually block studs and nuts, or does the oil fill press fit into the block, Dodge military engines used a bolted on oil filler tube. Carter