I don't own a StepDown but I believe the latch is similar to many other cars of the same era.

Here's a latch from a Plymouth.

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The latch mechanism is mounted to the stamped steel plate in the center that's bolted to the top of the baffle. A plunger on the underside of your hood, drops down into the round hole. The flat metal latch fits around it tightly (like a guillotine) and prevents the hood from opening.  That flat, sideways-pivoting lever to the right, is part of that latch and it is attached to the hood release cable (you can see the cable heading off towards the 1 o'clock position).  If only you could reach through the grille below this, and pull that lever, the hood wood open.  But you can't reach up there: The baffle backs up to the radiator. making it impossible to get your hand up there.

So I think you have two choices: 

First, going through the grille, see if you can  wedge a screwdriver between the plunger that is trapped by the latch, and the flat metal part that holds the plunger.  Then maybe you can force the latch away from the plunger until it releases the plunger.  While you are prying with the screwdriver, have someone push down hard on the hood, this will release the tension on the plunger and latch, and they may more easily separate from one another.

Second: some versions of this type of latch have a bent metal portion of the latch dropping down through a slot in the mounting plate, so that it is accessible from beneath.  You can try to pry THAT with a screwdriver from below, to make the latch pivot away from the plunger. Here also, always apply downward pressure to the hood to release the tension.  

Got it Jon, many thanks! 

I threw the  cable connection away and made a lever  to fit the mechanism,  that you reach under the right hand side of the  emblem  and move it to open the  hood.