This is more of an aesthetic question than a mechanical one. I wouldn't count on finding any ready-made KD hardware that would fit this application. If you're thinking of having big bolt heads showing on the table top, you can do that. I once made an executive desk -- similar size oval, in Brazilian rosewood -- with two hefty vertical slabs supporting it. To make the connection from the top to the "legs," I designed steel connectors, consisting of 1/4" thick steel plates that were securely screwed to the underside of the top, welded to 1/2" x 4" steel straps that went into deep sockets in the legs. Talk about rack resistant!
Engineering is an element in just about all furniture design. We make things to perform as intended, using available materials and resources. The important thing is to define your intention. Table legs, to me, are a lot like workbench legs: You don't want to have the table/bench wiggling around when you apply sideways forces to either horizontal axis. (You don't need to worry too much about the vertical dimension here; 6x6 legs could support a small truck.) So, the important thing is to provide an appropriate level of rack resistance. Deciding on what's appropriate is your design intent.
Making it happen might involve heavy duty hardware like I mentioned above, or it could be a more conventional table rail system, where the height of the rails is proportionate to the rack resistance they provide. You could make the rails knock-down by attaching them to the legs with sliding dovetails or some kind of cleverly-designed brackets, or maybe just angle iron segments screwed to leg and rail.