My install was an OEM 2-duct Heatercraft unit that I brought on Ebay from an MC owner who never had his installed.
You can see the edge of the heater core in the pic behind the battery. The visible hose comes around the battery to a hot tube under the observer's seat. The second hose which you can't see goes under the walkthru to an outlet at the driver's feet.
The hoses to and from the engine go under the floor through a cutout that was already there. You can barely see one on the bow side of the core. (The hose between the amps is the fresh air intake for the bilge.)
2005 X2, Viper Red, MCX, OJ TZ-X5 prop, PPass, rear 750 sacs, KBS, IBS, Bennett Wake Plate, custom wake shaper
(previous) 2001 X5, 1991 TriStar 190