A design philosophy to consider is to assist thermo-syphon effects. If both pump flow and "hot oil rising, cool oil falling effect" go in the same direction, then flow is better. I believe that the hot supply should go into the cooler at the top, and cold return out the bottom, just like a car coolant radiator.
The Parts Catalog indicates the left side line is the return.
Some Elvan siren in my brain always brings me back to the idea of mounting a Guzzi big-block on a "Moggie" trike. I do hope you will let us in on how your Triking comes along!
FWIW: I upgraded my '01 V11 Le Mans to Öhlins. Easy. Fits w/o adapting. Only thing that didn't fit anymore was the front mudguard and the front axle. I went for an early Aprilia RSV CF one and a Ducati 999 hollow front axle.