Sounds like it won't have any wood flavor, so I wouldn't enter it in that category. Enter it as what it tastes like.
It's still going to taste like a barrel aged beer, in my opinion. From a judging perspective I think the 33B is about the only place to put it. You could stretch and go for 34C experimental, but you're going to get lumped in with a bunch of other stuff and you're going to have to describe in great detail what the judges should be expecting.
I would go 33B and list it as "American Porter aged on(/with) Bourbon". The guidelines say you only have to give information about the type of wood and char level if it makes a big impact.
"Entry Instructions: The entrant must specify the additional
alcohol character, with information about the barrel if relevant
to the finished flavor profile. The entrant must specify the
base style;"
Is your beer "Wood Aged"... no... but based on flavor profile and judging perspective there's not another category where it would fit.
That's my interpretation of the guidelines.
Also, your feedback can guide you, if you plan to enter more than one. A good judge if they feel something is out of style, should recommend what category they think it should be. "This would be better suited as an XYZ."
Good luck!