Bourret,
If you have the manifold where you can see it just look into the carb intakes. I can't find that part number in any of my books either, but the dual plane and single plane are easy to tell by just looking. My 65 Ford with the 427 tunnel port had a single plane intake with dual 4s and the carbs set up quite high compared to a stock dual 4 intake. Also in the dual plane intake you should be able to look and see the double shelf or whatever technical term they use. One side of the carb will feed to the lower level and the other goes to the higher level. In a single plane intake you won't have that two levels, just one big gas guzzling gaping hole.
Ron
