To my knowledge Offy never built a dual plane. The 360* is the designation for a single plane. IIRC all of their V8 intakes were marked 360*.
I have one sitting on the top of my 360 in my work van. It has the 318 sized ports as the manifold I wanted was 340/360 specific. It ran fine with a Comp RV cam and pulled my 6200lb van hard to 5200RPM single exhaust, iron manifolds, and 850cfm Thermoquad.
It is an Offy 318 360* Dual Port. 2 sets of runners to each cylinder. 2 separate plenums. One for the primaries, and a bigger one for the secondaries.
